Progress toward an ERL extension to CESR

Hoffstaetter, Georg; Bazarov, Ivan; Bilderback, Donald H.; Codner, J.; Dunham, Bruce; Dale, Darren; Finkelstein, Ken; Förster, M.; Greenwald, S.; Grüner, Sol M.; Li, Y.; Liepe, Matthias; Mayes, Christopher; Sagan, D.; Sinclair, C. K.; Song, C.; Temnykh, A.; Tigner, M.; Xie, Yi

doi:10.1109/pac.2007.4440134

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…The intrinsic fast response of the QCL is compatible with the laser pulses tailored in optimum temporal profile and it is suitable for electron source of ultra-small emittance required in the future ERL light sources. (4) ，Argonne National Laboratory (5) が 5-7 GeV クラスの ERL 型 X 線放射光源の計画を進めている。晶した AlGaAs が量子効率と寿命の点で GaAs を上回ることが示され (17) ，また，GaAs/AlGaAs の超格子が小さな初期エミッタンスと高い量子効率を実現する可能性が示されている (18) 。本稿では，全く新しい可能性として，量子カスケードレーザー (QCL) の原理を応用して，高速応答性と小さな初期エミッタンスを両立する光陰極を提案する。 QCL は，THz 領域の新しい光源として研究が進んできた (19)…”

Section: Fig 1 Schematic View Of An Erl Light Sourceunclassified

High-Brightness Electron Sources for a Next Generation Light Source by an Energy Recovery Linac

Iijima

Nagai

Nishimori³

et al. 2009

IEEJ Trans.EIS

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A high-brightness electron source of ultra-small emittance and high-average current is one of the most important components for next-generation light sources based on an energy-recovery linac (ERL). Such a high-brightness electron source can be realized by a DC photo-cathode gun driven by laser pulses tailored in temporal and spatial dimensions. We propose a novel photocathode based on a quantum cascade laser (QCL). Since ultrafast response of photo-electron emission from the QCL is compatible with tailored laser pulses, it is a candidate for the electron source for ERLs.

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Section: Fig 1 Schematic View Of An Erl Light Sourceunclassified

High-Brightness Electron Sources for a Next Generation Light Source by an Energy Recovery Linac

Iijima

Nagai

Nishimori³

et al. 2009

IEEJ Trans.EIS

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“…3 are results of normalized emittance from simulations in BMAD through the ERL lattice with the calculated coupler kick values for both proposed Q ext values and for all six coupler configurations. The initial normalized emittance is 1 × 10 −7 m. The Cornell ERL is split into two accelerating sections, labeled as linac 1 and 2, connected by a return loop [16]. To compensate for overall transverse kicks, the necessary corrector coil strengths are computed and included in the lattice.…”

Section: A Single Cavitymentioning

confidence: 99%

Transverse emittance dilution due to coupler kicks in linear accelerators

Buckley

Hoffstaetter

2007

Phys. Rev. ST Accel. Beams

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One of the main concerns in the design of low emittance linear accelerators (linacs) is the preservation of beam emittance. Here we discuss one possible source of emittance dilution, the coupler kick, due to transverse electromagnetic fields in the accelerating cavities of the linac caused by the power coupler geometry. In addition to emittance growth, the coupler kick also produces orbit distortions. It is common wisdom that emittance growth from coupler kicks can be strongly reduced by using two couplers per cavity mounted opposite each other or by having the couplers of successive cavities alternation from above to below the beam pipe so as to cancel each individual kick. While this is correct, including two couplers per cavity or alternating the coupler location requires large technical changes and increased cost for superconducting cryomodules where cryogenic pipes are arranged parallel to a string of several cavities. We therefore analyze consequences of alternate coupler placements.We show here that alternating the coupler location from above to below compensates the emittance growth as well as the orbit distortions. And for sufficiently large Q values, alternating the coupler location from before to after the cavity leads to a cancellation of the orbit distortion but not of the emittance growth, whereas alternating the coupler location from before and above to behind and below the cavity cancels the emittance growth but not the orbit distortion. We show that cancellations hold for sufficiently large Q values. These compensations hold even when each cavity is individually detuned, e.g. by microphonics. Another effective method for reducing coupler kicks that is studied is the optimization of the phase of the coupler kick so as to minimize the effects on emittance from each coupler. This technique is independent of the coupler geometry but relies on operating on crest. A final technique studied is symmetrization of the cavity geometry in the coupler region with the addition of a stub opposite the coupler. This technique works by reducing the amplitude of the off axis fields and is thus effective for off crest acceleration as well.We show applications of these techniques to the energy recovery linac (ERL) planned at Cornell University.

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“…Bunches enter the ERL via the injector at (1). They are accelerated first by linac A at (2) and then by linac B at (4) after traversing the turn-around loop connecting the linacs at (3). They then traverse the Cornell Electron Storage Ring (CESR) at (6), producing x-rays in beamline sections (5) and (7).…”

Section: Introductionmentioning

confidence: 99%

“…Now, the bunch returns to linac A, the second turn-around loop, and linac B, which apply Eqs. (1), (2) and (3) to yield…”

Section: Introductionmentioning

confidence: 99%

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Compensation of wakefield-driven energy spread in energy recovery linacs

Hoffstaetter

Lau

2008

Phys. Rev. ST Accel. Beams

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Energy Recovery Linacs provide high-energy beams, but decelerate those beams before dumping them, so that their energy is available for the acceleration of new particles. During this deceleration, any relative energy spread that is created at high energy is amplified by the ratio between high energy and dump energy. Therefore, Energy Recovery Linacs are sensitive to energy spread acquired at high energy, e.g. from wake fields. One can compensate the time-correlated energy spread due to wakes via energy-dependent time-of-flight terms in appropriate sections of an Energy Recovery Linac, and via high-frequency cavities. We show that nonlinear time-of-flight terms can only eliminate odd orders in the correlation between time and energy, if these terms are created by a beam transport within the linac that is common for accelerating and decelerating beams. If these two beams are separated, so that different beam transport sections can be used to produce time-offlight terms suitable for each, also even-order terms in the energy spread can be eliminated. As an example, we investigate the potential of using this method for the Cornell x-ray Energy Recovery Linac. Via quadratic time-of-flight terms, the energy spread can be reduced by 66%. Alternatively, since the energy spread from the dominantly resistive wake fields of the analysed accelerator is approximately harmonic in time, a high-frequency cavity could diminish the energy spread by 81%. This approach would require bunch-lengthening and recompression in separate sections for accelerating and decelerating beams. Such sections have therefore been included in Cornell's x-ray Energy Recovery Linac design.

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Progress toward an ERL extension to CESR

Cited by 7 publications

References 11 publications

High-Brightness Electron Sources for a Next Generation Light Source by an Energy Recovery Linac

High-Brightness Electron Sources for a Next Generation Light Source by an Energy Recovery Linac

Transverse emittance dilution due to coupler kicks in linear accelerators

Compensation of wakefield-driven energy spread in energy recovery linacs

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