4 papers

title:	Photoinjector design for the LCLS
format:	conference procceeding
conference:	23rd International Free Electron Laser Conference
year:	2002
16 authors:	Bolton, P. R. | Clendenin, J. E. | Dowell, D. H. | M. Ferrario | Fisher, A. S. | Gierman, S. M. | Kirby, R. E. | P. Krejcik | Limborg, C. G. | Mulhollan, G. A. | D. Nguyen | D. T. Palmer | J. B. Rosenzweig | Schmerge, J. F. | L. Serafini | X. J. Wang
abstract:	The design of the Linac Coherent Light Source assumes that a low-emittance, 1 nC, 10 ps beam will be available for injection into the 15 GeV linac. The proposed RF photocathode injector that will meet this requirement is based on a 1.6-cell S-band RF gun equipped with an emittance-compensating solenoid. The booster accelerator with a gradient of 25 MV/m is positioned at the beam waist coinciding with the first emittance maximum, i.e., the "new working point." The UV pulses required for cathode excitation will be generated by tripling the output of a Ti:sapphire laser system. Details of the design and the supporting simulations are presented. (12 References).
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title:	New design study and related experimental program for the LCLS RF photoinjector
format:	conference procceeding
conference:	2000 European Particle Accelerator Conference
year:	2000
11 authors:	M. Ferrario | Bolton, P. R. | Clendenin, J. E. | Dowell, D. H. | Gierman, S. M. | M. E. Hernandez | D. Nguyen | D. T. Palmer | J. B. Rosenzweig | Schmerge, J. F. | L. Serafini
abstract:	We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that lead to the discovery of a new effective working point for a split RF photoinjector. We consider the emittance compensation regime of a space charge beam: by increasing the solenoid strength, the emittance evolution shows a double minimum behavior in the drifting region. If the booster is located where the relative emittance maximum and the envelope waist occur, the second emittance minimum can be shifted to the booster exit and frozen at a very low level (0.3 mm-mrad for a 1 nC flat top bunch), to the extent that the invariant envelope matching conditions are satisfied. Standing Wave Structures or alternatively Traveling Wave Structures embedded in a Long Solenoid are both candidates as booster linac. A careful measurement of the emittance evolution as a function of position in the drifting region is necessary to verify the computation and to determine experimentally the proper position of the booster cavities. The new design study and supporting experimental program under way at the SLAC Gun Test Facility are discussed.
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title:	HOMDYN study for the LCLS RF photo-injector
format:	conference procceeding
conference:	2nd ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams
year:	2000
5 authors:	M. Ferrario | Clendenin, J. E. | D. T. Palmer | J. B. Rosenzweig | L. Serafini
abstract:	We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that led to the discovery of a new effective working point for a split RF photoinjector. The HOMDYN code, the main simulation tool adopted in this work, is described together with its recent improvements. The new working point and its LCLS application is discussed. Validation tests of the HOMDYN model and low emittance predictions, 0.3 mm-mrad for a 1 nC flat top bunch, are performed with respect to the multi-particle tracking codes ITACA and PARMELA. (26 References).
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title:	The design for the LCLS RF photoinjector
format:	conference procceeding
conference:	20th International Free Electron Laser Conference
year:	1999
16 authors:	Alley, R. | Bharadwaj, V. | Clendenin, J. E. | P. Emma | Fisher, A. | Frisch, J. | Kotseroglou, T. | R. H. Miller | D. T. Palmer | Schmerge, J. F. | Sheppard, J. C. | Woodley, M. | Yeremian, A. D. | J. B. Rosenzweig | D. Meyerhofer | L. Serafini
abstract:	We report on the design of the RF photoinjector of the Linac Coherent Light Source. The RF photoinjector is required to produce a single 150 MeV bunch of similar to 1 nC and similar to 100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of similar to 1 pi mm-mrad. The design employs a 1.6-cell S-band RF gun with an optical spot size at the cathode of a radius of similar to 1 mm and a pulse duration with an rms sigma of similar to 3 ps. The peak RF field at the cathode is 150 MV/m with extraction 57 degrees ahead of the RF peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency, the laser wavelength for a Cu cathode should be tunable around 260 nm. Following the injection linac the geometric emittance simply damps linearly with energy growth. PARMELA simulations show that this design will produce the desired normalized emittance, which is about a factor of two lower than has been achieved to date in other systems. In addition to low emittance, we also aim for laser amplitude stability of 1% in the UV and a timing jitter in the electron beam of 0.5 ps rms, which will lead to less than 10% beam intensity fluctuation after the electron bunch is compressed in the main linac.
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