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Vortex lattices in dipolar two-component Bose-Einstein condensates
Dergi Makalesi

Dergi Makalesi
Kaynak :
DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
N. Ghazanfari , A. Keles , M. O. Oktel
Konu :
OPTİK, Atom ve Molekül Fiziği, Elektromanyetizma, Akustik, Isı Transferi, Klasik Mekanik ve Akışkanlar Dinamiği, Optik, Temel Bilimler, Fizik, Temel Bilimler (SCI), FİZİKSEL, ATOMİK, MOLEKÜLER VE KİMYASAL
Yıl :
2014
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
We consider a rapidly rotating two-component Bose-Einstein condensate with short-range s-wave interactions as well as dipolar coupling. We calculate the phase diagram of vortex lattice structures as a function of the intercomponent s-wave interaction and the strength of the dipolar interaction. We find that the long-range interactions cause new vortex lattice structures to be stable and lead to a richer phase diagram. Our results reduce to the previously found lattice structures for short-range interactions and single-component dipolar gases in the corresponding limits.
Anahtar Kelimeler : OPTİK, Atom ve Molekül Fiziği, Elektromanyetizma, Akustik, Isı Transferi, Klasik Mekanik ve Akışkanlar Dinamiği, Optik, Temel Bilimler, Fizik, Temel Bilimler (SCI), FİZİKSEL, ATOMİK, MOLEKÜLER VE KİMYASAL, Makale

ISSN: 1050-2947
Sınıflandırma :
Fizik %100
2
Spinal Enstrümantasyon
Kitap Bölümü

Kitap Bölümü
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DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
Saffet TÜZGEN , Mehmet Murat HANCI
Konu :
Sağlık Bilimleri, Tıp, Klinik Tıp (MED)
Yıl :
2021
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
Anahtar Kelimeler : Sağlık Bilimleri, Tıp, Klinik Tıp (MED), Kitapta Bölüm
Sınıflandırma :
3
Ayvansaray’da Üç Yapı: Hatice Sultan Sıbyan Mektebi, Sebil ve Çeşmesi
Bildiri Serisi

Bildiri Serisi
Kaynak :
DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
AKÇIL HARMANKAYA , Nesrin Çiçek
Konu :
Sanat ve Beşeri Bilimler, Sanat ve Beşeri Bilimler (AHCI), Sosyal ve Beşeri Bilimler
Yıl :
2021
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
Anahtar Kelimeler : Sanat ve Beşeri Bilimler, Sanat ve Beşeri Bilimler (AHCI), Sosyal ve Beşeri Bilimler, Bildiri
Sınıflandırma :
Mimarlık %100
4
Oral and Craniofacial manifestations of Ellis-Van Creveld syndrome
Bildiri Serisi

Bildiri Serisi
Kaynak :
DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
FIGEN SEYMEN
Yıl :
2021
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
Anahtar Kelimeler : Bildiri
Sınıflandırma :
5
Oral Kematerapötik ilaçlara bağlı geç tip hipersensitivite reaksiyonlarında on altı günlük desensitizasyon protokolü
Bildiri Serisi

Bildiri Serisi
Kaynak :
DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
SUNA BUYUKORTURK , M OLGAC , R COSKUN , SEMRA DEMİR , Aslı GELINCIK , BAHATTIN COLAKOĞLU , D. UNAL
Konu :
Klinik Tıp (MED), Tıp, Sağlık Bilimleri
Yıl :
2021
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
Anahtar Kelimeler : Klinik Tıp (MED), Tıp, Sağlık Bilimleri, Bildiri
Sınıflandırma :
6
Demixing in mesoscopic boson-fermion clouds inside cylindrical harmonic traps: Quantum phase diagram and role of temperature
Dergi Makalesi

Dergi Makalesi
Kaynak :
DSpace Makaleler
Yayıncı :
PHYSICAL REVIEW A
Yazar(lar) :
A Minguzzi , MP Tosi , P Vignolo , Z Akdeniz
Konu :
Elektromanyetizma, Akustik, Isı Transferi, Klasik Mekanik ve Akışkanlar Dinamiği, Temel Bilimler, Optik, Atom ve Molekül Fiziği, FİZİKSEL, ATOMİK, MOLEKÜLER VE KİMYASAL, Temel Bilimler (SCI), Fizik, OPTİK
Yıl :
2002
PHYSICAL REVIEW A
Yayıncı Web Sitesi
Kaydet
We use a semiclassical three-fluid model to evaluate the phenomena of spatial demixing in mesoscopic clouds of fermionic and bosonic atoms at high dilution under harmonic confinement. We assume repulsive boson-boson and boson-fermion interactions and include a bosonic thermal cloud at finite temperature T. The finite system size allows three different regimes for the equilibrium density profiles at T=0: a fully mixed state, a partially mixed state in which the overlap between bosons and fermions is decreasing, and a fully demixed state where the two clouds have zero overlap. We propose simple analytical rules for the two crossovers between the three regimes as functions of the system parameters and support these rules by extensive numerical calculations. A universal phase diagram is shown to be valid for the transition to the regime of full demixing, where we identify several exotic configurations in addition to simple ones consisting of a core of bosons enveloped by fermions and vice versa. With increasing temperature some exotic configurations are transformed into more symmetric ones, until demixing is ultimately lost. For very high values of the boson-fermion repulsion we also report demixing between the fermions and the thermally excited bosons.
Anahtar Kelimeler : Elektromanyetizma, Akustik, Isı Transferi, Klasik Mekanik ve Akışkanlar Dinamiği, Temel Bilimler, Optik, Atom ve Molekül Fiziği, FİZİKSEL, ATOMİK, MOLEKÜLER VE KİMYASAL, Temel Bilimler (SCI), Fizik, OPTİK, Makale

ISSN: 2469-9926
Sınıflandırma :
7
Low energy tertiary beam line design for the CERN neutrino platform project
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
N. Charitonidis , I. Efthymiopoulos
Yıl :
2017
Physical Review Accelerators and Beams
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In the framework of CERN neutrino platform project at the CERN SPS North Area, two new beam lines have been designed as extensions of the existing secondary beam lines, able to provide low energy particles in the momentum range of 0.4 to 12  GeV/c. The layout of these very low energy beam lines, their design parameters as well as outlook on their expected performance, are summarized in this paper.
DOI : 10.1103/PhysRevAccelBeams.20.111001
ISSN: 2469-9888
Cilt: 20
Sayı: 11
Sayfa: 111001
Sınıflandırma :
8
Direct observation of breakdown trigger seeds in a normal-conducting rf accelerating cavity
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Tetsuo Abe , Tatsuya Kageyama , Hiroshi Sakai , Yasunao Takeuchi , Kazuo Yoshino
Yıl :
2018
Physical Review Accelerators and Beams
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In our previous study on a normal-conducting 508.9-MHz continuous-wave accelerating cavity, it was discovered that most breakdown events were accompanied by the explosion of a stable bright spot on one of the two end plates of the cavity (Breakdown Type I) or by a spot-type explosion not originating from a stable bright spot (Breakdown Type II); both of these explosions can be understood as breakdown triggers. In the present study, the light emitters of stable bright spots in Breakdown Type I and the dynamics of spot-type explosions in Breakdown Type II were investigated using hyperspectral and high-speed cameras, respectively, during high-power test.
DOI : 10.1103/PhysRevAccelBeams.21.122002
ISSN: 2469-9888
Cilt: 21
Sayı: 12
Sayfa: 122002
Sınıflandırma :
9
Three-dimensional envelope instability in periodic focusing channels
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Ji Qiang
Yıl :
2018
Physical Review Accelerators and Beams
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Kaydet
The space-charge driven envelope instability can be of great danger in high intensity accelerators and was studied using a two-dimensional (2D) envelope model and three-dimensional (3D) macroparticle simulations before. In this paper, we study the instability for a bunched beam using a three-dimensional envelope model in a periodic solenoid and radio-frequency (rf) focusing channel and a periodic quadrupole and rf focusing channel. This study shows that when the transverse zero current phase advance is below 90°, the beam envelope can still become unstable if the longitudinal zero current phase advance is beyond 90°. For the transverse zero current phase advance beyond 90°, the instability stopband width becomes larger with the increase of the longitudinal focusing strength and even shows different structure from the 2D case when the longitudinal zero current phase advance is beyond 90°. Breaking the symmetry of two longitudinal focusing rf cavities and the symmetry between the horizontal focusing and the vertical focusing in the transverse plane in the periodic quadrupole and rf channel makes the instability stopband broader. This suggests that a more symmetric accelerator lattice design might help reduce the range of the envelope instability in parameter space.
DOI : 10.1103/PhysRevAccelBeams.21.034201
ISSN: 2469-9888
Cilt: 21
Sayı: 3
Sayfa: 034201
Sınıflandırma :
10
Impact of process parameters and design options on heat leaks of straight cryogenic distribution lines
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
P. Duda , M. Chorowski , J. Polinski
Yıl :
2017
Physical Review Accelerators and Beams
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The Future Circular Collider (FCC) accelerator will require a helium distribution system that will exceed the presently exploited transfer lines by almost 1 order of magnitude. The helium transfer line will contain five process pipes protected against heat leaks by a common thermal shield. The design pressure of the FCC process pipe with supercritical helium will be equal to 5.0 MPa, significantly exceeding the 2.0 MPa value in the present, state-of–art transfer lines. The increase of the design pressure requires construction changes to be introduced to the support system, the vacuum barriers and the compensation bellows. This will influence heat flows to the helium. The paper analyses the impact of the increased design pressure on the heat flow. The paper also offers a discussion of the design modifications to the compensation system, including the replacement of stainless steel with Invar®—aimed at mitigating the pressure increase.
DOI : 10.1103/PhysRevAccelBeams.20.033202
ISSN: 2469-9888
Cilt: 20
Sayı: 3
Sayfa: 033202
Sınıflandırma :
11
Performance of a second generation X-band rf photoinjector
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
R.u2009A. Marsh , G.u2009G. Anderson , S.u2009G. Anderson , D.u2009J. Gibson , C.u2009P.u2009J. Barty , Y. Hwang
Yıl :
2018
Physical Review Accelerators and Beams
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Kaydet
rf photoinjectors produce incredibly bright electron beams enabling advanced photon science applications such as the current generation of free electron lasers and high energy x-rays and gamma-rays via laser-Compton scattering. A second generation 5.59 cell X-band rf gun has been developed, installed, conditioned, commissioned, tuned, and used to produce laser-Compton x-rays and multiple electron bunches. A charge per bunch from a few pC to 500 pC has been measured, consistent with a quantum efficiency of 5×10^{-5} using a 263 nm 10 Hz photocathode drive laser. The rf gun has operated close to design performance at high gradient, and more reliably at lower gradient achieving a root mean square normalized emittance of 0.3 mm mrad at both 80 pC at 185  MV/m, and 40 pC at 165  MV/m. Thermal emittance is estimated at 0.55  mm mrad/mm. Energy spread of 0.03% has been achieved. These results agree very well with modeling predictions for the operating conditions under which the measurements were made. Unusually disruptive breakdowns were observed with an applied magnetic field of 0.5T used for emittance compensation.
DOI : 10.1103/PhysRevAccelBeams.21.073401
ISSN: 2469-9888
Cilt: 21
Sayı: 7
Sayfa: 073401
Sınıflandırma :
12
High efficiency, multiterawatt x-ray free electron lasers
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
C. Emma , K. Fang , J. Wu , C. Pellegrini
Yıl :
2016
Physical Review Accelerators and Beams
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In this paper we present undulator magnet tapering methods for obtaining high efficiency and multiterawatt peak powers in x-ray free electron lasers (XFELs), a key requirement for enabling 3D atomic resolution single molecule imaging and nonlinear x-ray science. The peak power and efficiency of tapered XFELs is sensitive to time dependent effects, like synchrotron sideband growth. To analyze this dependence in detail we perform a comparative numerical optimization for the undulator magnetic field tapering profile including and intentionally disabling these effects. We show that the solution for the magnetic field taper profile obtained from time independent optimization does not yield the highest extraction efficiency when time dependent effects are included. Our comparative optimization is performed for a novel undulator designed specifically to obtain TW power x-ray pulses in the shortest distance: superconducting, helical, with short period and built-in strong focusing. This design reduces the length of the breaks between modules, decreasing diffraction effects, and allows using a stronger transverse electron focusing. Both effects reduce the gain length and the overall undulator length. We determine that after a fully time dependent optimization of a 100 m long Linac coherent light source-like XFEL we can obtain a maximum efficiency of 7%, corresponding to 3.7 TW peak radiation power. Possible methods to suppress the synchrotron sidebands, and further enhance the FEL peak power, up to about 6 TW by increasing the seed power and reducing the electron beam energy spread, are also discussed.
DOI : 10.1103/PhysRevAccelBeams.19.020705
ISSN: 2469-9888
Cilt: 19
Sayı: 2
Sayfa: 020705
Sınıflandırma :
13
Ion acceleration by fs laser in target-normal-sheath-acceleration regime and comparison of time-of-flight spectra with particle-in-cell simulations
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
L. Torrisi , G. Costa
Yıl :
2020
Physical Review Accelerators and Beams
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The ions acceleration through an fs laser irradiating a reduced graphene oxide foil in a target-normal-sheath-acceleration regime is investigated using a SiC detector connected in time-of-flight configuration. The experimental data indicated maximum proton energy of 1.8 MeV and a large number of carbon ions accelerated at different energies depending on their charge state. Particle-in-cell (PIC) simulations were applied to the studied target given the electron density as a function of the space and time and permitted one to evaluate the electrical field developed in the rear side of the foil driving the forward ion acceleration. The simulation indicates that the carbon ions are subjected to a lower acceleration with respect to protons, due to their slow velocity, depending on the charge-to-mass ratio. The latter does not permit carbon ions to be affected by the maximum electric field but a lower intensity due to the fast time decay of the electric field. Considering the angular emission of protons and the six carbon ions, the charge particles assume a Boltzmann energy distribution with a fixed cutoff at high energy, in agreement with the experimental measurements of ion energy.
DOI : 10.1103/PhysRevAccelBeams.23.011304
ISSN: 2469-9888
Cilt: 23
Sayı: 1
Sayfa: 011304
Sınıflandırma :
14
Transient beam loading and rf power evaluation for future circular colliders
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Ivan Karpov , Philippe Baudrenghien
Yıl :
2019
Physical Review Accelerators and Beams
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Kaydet
Interaction of the beam with the fundamental impedance of the accelerating cavities can limit the performance of high-current accelerators. It can result in a significant variation of bunch-by-bunch parameters (bunch length, synchronous phase, etc.) if filling patterns contain gaps that are not negligible compared with the cavity filling time. In the present work, this limitation is analyzed using the steady-state time-domain approach for the high-current option (Z) of the future circular electron-positron collider and for the future circular hadron-hadron collider. Mitigation of transient beam loading by direct rf feedback is addressed with evaluation of additional required generator power.
DOI : 10.1103/PhysRevAccelBeams.22.081002
ISSN: 2469-9888
Cilt: 22
Sayı: 8
Sayfa: 081002
Sınıflandırma :
15
Vacuum electrical breakdown conditioning study in a parallel plate electrode pulsed dc system
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Anders Korsbäck , Flyura Djurabekova , Laura Mercadé Morales , Iaroslava Profatilova , Enrique Rodriguez Castro , Walter Wuensch , Sergio Calatroni , Tommy Ahlgren
Yıl :
2020
Physical Review Accelerators and Beams
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Conditioning of a metal structure in a high-voltage system is the progressive development of resistance to vacuum arcing over the operational life of the system. This is, for instance, seen during the initial operation of radio frequency (rf) cavities in particle accelerators. It is a relevant topic for any technology where breakdown limits performance and where conditioning continues for a significant duration of system run time. Projected future linear accelerators require structures with accelerating gradients of up to 100  MV/m. Currently, this performance level is achievable only after a multimonth conditioning period. In this work, a pulsed dc system applying voltage pulses over parallel disk electrodes was used to study the conditioning process, with the objective of obtaining insight into its underlying mechanics and, ultimately, to find ways to shorten the conditioning process. Two kinds of copper electrodes were tested: as-prepared machine-turned electrodes (“hard” copper) and electrodes that additionally had been subjected to high-temperature treatments (“soft” copper). The conditioning behavior of the soft electrodes was found to be similar to that of comparably treated accelerating structures, indicating a similar conditioning process. The hard electrodes reached the same ultimate performance as the soft electrodes much faster, with a difference of more than an order of magnitude in the number of applied voltage pulses. Two distinctly different distributions of breakdown locations were observed on the two types of electrodes. Considered together, our results support the crystal structure dislocation theory of breakdown and suggest that the conditioning of copper in high field systems such as rf accelerating structures is dominated by material hardening.
DOI : 10.1103/PhysRevAccelBeams.23.033102
ISSN: 2469-9888
Cilt: 23
Sayı: 3
Sayfa: 033102
Sınıflandırma :
16
Spatial control of photoemitted electron beams using a microlens-array transverse-shaping technique
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
A. Halavanau , G. Qiang , G. Ha , E. Wisniewski , P. Piot , J.u2009G. Power , W. Gai
Yıl :
2017
Physical Review Accelerators and Beams
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A transversely inhomogeneous laser distribution on the photocathode surface generally produces electron beams with degraded beam quality. In this paper, we explore the use of microlens arrays to dramatically improve the transverse uniformity of an ultraviolet drive-laser pulse used in a photoinjector. We also demonstrate a capability of microlens arrays to generate transversely modulated electron beams and present an application of such a feature to diagnose the properties of a magnetized beam.
DOI : 10.1103/PhysRevAccelBeams.20.103404
ISSN: 2469-9888
Cilt: 20
Sayı: 10
Sayfa: 103404
Sınıflandırma :
17
Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
P. Lee , G. Maynard , T.u2009L. Audet , B. Cros , R. Lehe , J.-L. Vay
Yıl :
2016
Physical Review Accelerators and Beams
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The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ∼11% can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while the electron energy can be finely tuned in the last acceleration section.
DOI : 10.1103/PhysRevAccelBeams.19.112802
ISSN: 2469-9888
Cilt: 19
Sayı: 11
Sayfa: 112802
Sınıflandırma :
18
Design and optimization of Compact Linear Collider main linac accelerating structure
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Hao Zha , Alexej Grudiev
Yıl :
2016
Physical Review Accelerators and Beams
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Kaydet
The Compact Linear Collider (CLIC) main linac uses waveguide damped structure as its baseline design. The current baseline structure design written in the CLIC Conceptual Design Report is named “CLIC-G.” Recent activities on the CLIC-G design including high power tests on structure prototypes and the study of machining cost assessment had raised the need of reoptimizing the structure design to minimize the machining cost and the pulse surface temperature rise. This work presents optimization of the structure geometry, high-order-mode (HOM) damping loads and the design of a HOM-free power splitter for the input coupler. Compared to the current baseline design CLIC-G, the new structure design reduced the pulse surface temperature rise, input power and manufacturing cost and achieves better suppression to the long range transverse wakefield. Cell disks and damping loads for the new structure design are also more compact than those of the CLIC-G design.
DOI : 10.1103/PhysRevAccelBeams.19.111003
ISSN: 2469-9888
Cilt: 19
Sayı: 11
Sayfa: 111003
Sınıflandırma :
19
Combined zero degree structure beam dynamics and applications
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Ulrich Ratzinger , Hendrik Hähnel , Rudolf Tiede , Jan Kaiser , Ali Almomani
Yıl :
2019
Physical Review Accelerators and Beams
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The combined zero degree structure (KONUS) is a quasiperiodic structure. It was developed for the low-energy part of multigap drift tube linacs with H-type cavities. Their rf efficiency depends very much on a low electrical capacity of the drift tube structure, while in E-type structures like the Alvarez-DTL this is a minor effect. Therefore, instead of having quadrupole singlets integrated in voluminous drift tubes, KONUS allows one to develop a separated function drift tube linac (DTL) with a large voltage gain between two lenses. Very low beam injection energies can be realized, as the drift tube lengths can range down to around 10 mm. One KONUS period consists of a triplet lens, a rebuncher with a few gaps at a synchronous phase around −35°, and the main multigap acceleration designed for a hypothetical zero degree synchronous particle. The longitudinal beam dynamics along this main acceleration section and the layout of the quadrupole triplet channel are explained in detail. Two examples for pulsed high current proton and heavy ion acceleration are included.
DOI : 10.1103/PhysRevAccelBeams.22.114801
ISSN: 2469-9888
Cilt: 22
Sayı: 11
Sayfa: 114801
Sınıflandırma :
20
Beam measurement of the high frequency impedance sources with long bunches in the CERN Super Proton Synchrotron
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
A. Lasheen , T. Argyropoulos , T. Bohl , J.u2009F. Esteban Müller , H. Timko , E. Shaposhnikova
Yıl :
2018
Physical Review Accelerators and Beams
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Microwave instability in the Super Proton Synchrotron (SPS) at CERN is one of the main limitations to reach the requirements for the High Luminosity-LHC project (increased beam intensity by a factor 2). To identify the impedance source responsible of the instability, beam measurements were carried out to probe the SPS impedance. The method presented in this paper relies on measurements of the unstable spectra of single bunches, injected in the SPS with the rf voltage switched off. The modulation of the bunch profile gives information about the main impedance sources driving microwave instability, and is compared to particle simulations using the SPS impedance model to identify the most important contributions. This allowed us to identify the vacuum flanges as the main impedance source for microwave instability in the SPS, and to evaluate possible missing impedance sources.
DOI : 10.1103/PhysRevAccelBeams.21.034401
ISSN: 2469-9888
Cilt: 21
Sayı: 3
Sayfa: 034401
Sınıflandırma :
21
Laser pulsing in linear Compton scattering
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
G.u2009A. Krafft , E. Johnson , K. Deitrick , B. Terzić , R. Kelmar , T. Hodges , W. Melnitchouk , J.u2009R. Delayen
Yıl :
2016
Physical Review Accelerators and Beams
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Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions “in collision.” The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse Compton source. Many of the results allow easy scaling estimates to be made of the expected spectrum.
DOI : 10.1103/PhysRevAccelBeams.19.121302
ISSN: 2469-9888
Cilt: 19
Sayı: 12
Sayfa: 121302
Sınıflandırma :
22
rf surface impedance of a two-band superconductor
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Binping Xiao , C.u2009E. Reece
Yıl :
2019
Physical Review Accelerators and Beams
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In this paper, we extend the Mattis-Bardeen theory to obtain the surface impedance of a two-band superconductor, and apply it to magnesium diboride (MgB_{2}) for radiofrequency (rf) superconductivity applications. The numerical results for MgB_{2} are in good agreement with the previously published experimental results. The surface impedance properties are clearly dominated by the smaller gap, significantly limiting utility in the 10-20 K regime that might otherwise have been attractive.
DOI : 10.1103/PhysRevAccelBeams.22.053101
ISSN: 2469-9888
Cilt: 22
Sayı: 5
Sayfa: 053101
Sınıflandırma :
23
Storage ring two-color free-electron laser
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
J. Yan , H. Hao , J.u2009Y. Li , S.u2009F. Mikhailov , V.u2009G. Popov , N.u2009A. Vinokurov , S. Huang , J. Wu , S. Günster , Y.u2009K. Wu
Yıl :
2016
Physical Review Accelerators and Beams
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We report a systematic experimental study of a storage ring two-color free-electron laser (FEL) operating simultaneously in the infrared (IR) and ultraviolet (UV) wavelength regions. The two-color FEL lasing has been realized using a pair of dual-band high-reflectivity FEL mirrors with two different undulator configurations. We have demonstrated independent wavelength tuning in a wide range for each lasing color, as well as harmonically locked wavelength tuning when the UV lasing occurs at the second harmonic of the IR lasing. Precise power control of two-color lasing with good power stability has also been achieved. In addition, the impact of the degradation of FEL mirrors on the two-color FEL operation is reported. Furthermore, we have investigated the temporal structures of the two-color FEL beams, showing simultaneous two-color micropulses with their intensity modulations displayed as FEL macropulses.
DOI : 10.1103/PhysRevAccelBeams.19.070701
ISSN: 2469-9888
Cilt: 19
Sayı: 7
Sayfa: 070701
Sınıflandırma :
24
Fast mapping of terahertz bursting thresholds and characteristics at synchrotron light sources
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Miriam Brosi , Johannes L. Steinmann , Edmund Blomley , Erik Bründermann , Michele Caselle , Nicole Hiller , Benjamin Kehrer , Yves-Laurent Mathis , Michael J. Nasse , Lorenzo Rota , Manuel Schedler , Patrik Schönfeldt , Marcel Schuh , Markus Schwarz , Marc Weber , Anke-Susanne Müller
Yıl :
2016
Physical Review Accelerators and Beams
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Dedicated optics with extremely short electron bunches enable synchrotron light sources to generate intense coherent THz radiation. The high degree of spatial compression in this so-called low-α_{c} optics entails a complex longitudinal dynamics of the electron bunches, which can be probed studying the fluctuations in the emitted terahertz radiation caused by the microbunching instability (“bursting”). This article presents a “quasi-instantaneous” method for measuring the bursting characteristics by simultaneously collecting and evaluating the information from all bunches in a multibunch fill, reducing the measurement time from hours to seconds. This speed-up allows systematic studies of the bursting characteristics for various accelerator settings within a single fill of the machine, enabling a comprehensive comparison of the measured bursting thresholds with theoretical predictions by the bunched-beam theory. This paper introduces the method and presents first results obtained at the ANKA synchrotron radiation facility.
DOI : 10.1103/PhysRevAccelBeams.19.110701
ISSN: 2469-9888
Cilt: 19
Sayı: 11
Sayfa: 110701
Sınıflandırma :
25
Measurement of rf voltage in long traveling wave accelerating structures with application to the CERN Super Proton Synchrotron
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Patrick Kramer , Christine Vollinger
Yıl :
2019
Physical Review Accelerators and Beams
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Since its inauguration in 1976, the Super Proton Synchrotron (SPS) at CERN relies on a traveling wave system for particle acceleration instead of making use of standing wave cavities that are more common in circular accelerators. These traveling wave structures (TWSs) are essentially periodically loaded waveguides operated at a fundamental frequency of about 200 MHz. In the frame of the LHC injector upgrade project, the SPS accelerating system is presently improved to better cope with the increased beam intensity required for the future High Luminosity LHC era. The available accelerating voltage provided by the TWSs by means of radio-frequency (rf) generators is a fundamental and valuable input for machine operation and particle tracking codes used to simulate beam phenomena in the SPS. Measurement of the voltage with well known nonresonant and on-axis perturbation methods is however infeasible due to the extreme mechanical length of the SPS structures. It is shown that a good estimate of the rf voltage can be obtained from off-axis measurement samples in each accelerating gap in addition to the in- and output reflection coefficients of the structures. The rf voltage for the LHC proton beam delivered by the system configuration that was installed during the first and second exploitation run of the LHC is measured by this method, not including the beam loading. The impact on the fundamental accelerating mode and the rf voltage of additional higher order mode (HOM) couplers, which are also required for the upgrade of the acceleration system, is assessed by the proposed method as well.
DOI : 10.1103/PhysRevAccelBeams.22.101002
ISSN: 2469-9888
Cilt: 22
Sayı: 10
Sayfa: 101002
Sınıflandırma :
26
Reinforcement learning based schemes to manage client activities in large distributed control systems
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Y. Gao , J. Chen , T. Robertazzi , K.u2009A. Brown
Yıl :
2019
Physical Review Accelerators and Beams
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Kaydet
Large distributed control systems typically can be modeled by a hierarchical structure with two physical layers: console level computers (CLCs) layer and front end computers (FECs) layer. The control system of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) consists of more than 500 FECs, each acting as a server providing services to a large number of clients. Hence the interactions between the server and its clients become crucial to the overall system performance. There are different scenarios of the interactions. For instance, there are cases where the server has a limited processing ability and is queried by a large number of clients. Such cases can put a bottleneck in the system, as heavy traffic can slow down or even crash a system, making it momentarily unresponsive. Also, there are cases where the server has adequate ability to process all the traffic from its clients. We pursue different goals in those cases. For the first case, we would like to manage clients’ activities so that their requests are processed by the server as much as possible and the server remains operational. For the second case, we would like to explore an operation point at which the server’s resources get utilized efficiently. Moreover, we consider a real-world time constraint to the above case. The time constraint states that clients expect the responses from the server within a time window. In this work, we analyze those cases from a game theory perspective. We model the underlying interactions as a repeated game between clients, which is carried out in discrete time slots. For clients’ activity management, we apply a reinforcement learning procedure as a baseline to regulate clients’ behaviors. Then we propose a memory scheme to improve its performance. Next, depending on different scenarios, we design corresponding reward functions to stimulate clients in a proper way so that they can learn to optimize different goals. Through extensive simulations, we show that first, the memory structure improves the learning ability of the baseline procedure significantly. Second, by applying appropriate reward functions, clients’ activities can be effectively managed to achieve different optimization goals.
DOI : 10.1103/PhysRevAccelBeams.22.014601
ISSN: 2469-9888
Cilt: 22
Sayı: 1
Sayfa: 014601
Sınıflandırma :
27
Novel method for the generation of stable radiation from free-electron lasers at high repetition rates
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
Sven Ackermann , Bart Faatz , Vanessa Grattoni , Mehdi Mohammad Kazemi , Tino Lang , Christoph Lechner , Georgia Paraskaki , Johann Zemella , Gianluca Geloni , Svitozar Serkez , Takanori Tanikawa , Wolfgang Hillert
Yıl :
2020
Physical Review Accelerators and Beams
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For more than a decade free-electron lasers (FELs) have been in operation, providing scientists from many disciplines with the benefits of ultrashort, nearly transversely coherent radiation pulses with wavelengths down to the Ångstrom range. If no further techniques are applied, the FEL will only amplify radiation from the stochastic distributed electron density in the electron bunch. Contemporary developments aim at producing stable and single-mode radiation by preparing an electron bunch with favorable longitudinal electron density distributions using magnets and conventional laser pulses (seed), hence the name “seeding.” In recent years, short wavelength FELs at high electron beam energies and high repetition rates were proposed and built. At those repetition rates, an external seed with sufficient power to manipulate the electron beam cannot be provided by present state-of-the-art laser systems, thus no external seeding scheme could be applied yet. In this paper, we present ways to seed FELs to generate short wavelength radiation at high repetition rates, making use of tested electron beam manipulation schemes. For our parameter study, we used the parameters of FLASH, the free-electron laser in Hamburg. First simulations are presented, showing the feasibility of the method proposed.
DOI : 10.1103/PhysRevAccelBeams.23.071302
ISSN: 2469-9888
Cilt: 23
Sayı: 7
Sayfa: 071302
Sınıflandırma :
28
Fast radio frequency quadrupole envelope computation for model based beam tuning
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Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
O. Shelbaya , R. Baartman , O. Kester
Yıl :
2019
Physical Review Accelerators and Beams
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Efficient tuning of complex accelerator chains requires automated procedures, themselves reliant upon beam physical models. The Isotope Separator and ACcelerator (ISAC) facility at TRIUMF requires frequent changes of beam species (isotope), mass to charge ratio and beam energy tailored to experiment requirements, which demands rapid beam tuning. In addition, emergent effects such as long term changes of energy or energy spread require beam optimization that must be based on a complete model of the accelerator. Using an envelope code to build an end-to-end simulation of the accelerator facility for operational purposes reduces computing times by 3 or 4 orders of magnitude, when compared to particle tracking codes, so that the requisite simulations may be carried out in real time, by polling control system data. Herein described is the second order Hamiltonian for an radio frequency quadrupole (RFQ), presented within the framework of the envelope code transoptr. To benchmark the transoptr model, envelope simulations of the TRIUMF-ISAC RFQ have been performed and compared with the multiparticle code parmteq.
DOI : 10.1103/PhysRevAccelBeams.22.114602
ISSN: 2469-9888
Cilt: 22
Sayı: 11
Sayfa: 114602
Sınıflandırma :
29
Refined betatron tune measurements by mixing beam position data
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
P. Zisopoulos , Y. Papaphilippou , J. Laskar
Yıl :
2019
Physical Review Accelerators and Beams
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Kaydet
The measurement of the betatron tunes in a circular accelerator is of paramount importance due to their impact on beam dynamics. The resolution of the these measurements, when using turn-by-turn (TBT) data from beam position monitors, is greatly limited by the available number of turns in the signal. Because of decoherence from finite chromaticity and/or amplitude detuning, the transverse betatron oscillations appear to be damped in the TBT signal. On the other hand, an adequate number of samples is needed, if precise and accurate tune measurements are desired. In this paper, a method is presented that allows for very precise tune measurements within a very small number of turns. The theoretical foundation of this method is presented with results from numerical and tracking simulations and experimental TBT data which are recorded at electron and proton circular accelerators.
DOI : 10.1103/PhysRevAccelBeams.22.071002
ISSN: 2469-9888
Cilt: 22
Sayı: 7
Sayfa: 071002
Sınıflandırma :
30
Topological cathodes: Controlling the space charge limit of electron emission using metamaterials
Dergi Makalesi

Dergi Makalesi Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Yayıncı :
Physical Review Accelerators and Beams
Yazar(lar) :
David H. Dowell
Yıl :
2019
Physical Review Accelerators and Beams
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Kaydet
The space charge limit (SCL) of emission from photocathodes sets an upper limit on the performance of both high- and low-field electron guns. Generally, one is forced to strike a compromise between the space charge limit and the cathode’s intrinsic emittance [I. Bazarov et al., Phys. Rev. Lett. 102, 104801 (2009)PRLTAO0031-900710.1103/PhysRevLett.102.104801]. However, it is possible to nearly eliminate the SCL due to the image charge by engineering the topography of the cathode’s surface. A cathode with a surface plasma frequency below the frequency spectrum of the accelerating electrons will greatly reduce the polarization of the cathode and its image-charge field, thereby mitigating the cathode’s space charge limit for photoelectric, thermionic, and field emission. In the work presented here, a theory for the image-charge field of a disk of charge being accelerated from the cathode surface is developed which includes the frequency-dependent effects of the cathode’s dielectric function. This theory verifies the concept of SCL mitigation with a wire array metamaterial to design a metacathode with greatly reduced image-charge fields. The details of the holistic metacathode design spanning 6 orders of magnitude in scale are described.
DOI : 10.1103/PhysRevAccelBeams.22.084201
ISSN: 2469-9888
Cilt: 22
Sayı: 8
Sayfa: 084201
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