LINAC2014 - List of Authors (Citterio, A.)

Paper	Title	Page
MOPP118	C-Band Load Development for the High Power Test of the SwissFEL RF Pulse Compressor	329
	A. Citterio, J. Stettler, R. Zennaro PSI, Villigen PSI, Switzerland
	The SwissFEL C-band Linac will have 26 RF modules, each one consisting of a solid-state modulator and a 50 MW klystron that feeds a pulse compressor and four two meters long accelerating structures. The pulse compressor is of the Barrel Open Cavity type (BOC). A first prototype was successfully produced and high-power tested, reaching for full power klystron operation a peak power of 300 MW. For testing this BOC at maximum RF power, a broadband load was designed and built, based on a ridge waveguide design and high permeability stainless steel. Based on the experience gained at CERN for CLIC X-band high power loads, the RF design of the load was optimized to ensure high losses for a quite large range of magnetic steels. Test pieces were realized in three different magnetic steels to choose the best suited material commercially available. This paper reports about the RF design, material study, production and impressive high power results of this C-band load.

MOPP119	Measurements and High Power Test of the First C-band Accelerating Structure for SwissFEL	333
	R. Zennaro, J. Alex, A. Citterio, J.-Y. Raguin PSI, Villigen PSI, Switzerland
	The SwissFEL project is based on a 5.8 GeV C-band Linac which is composed of 10⁴ accelerating structures with a length of 2 m each. Due to the absence of dimple tuning no local frequency correction is possible and hence ultra-precise machining is required. The paper reports on both low level and high power RF test of the first nominal structure produced. The required mechanical precision has been reached and the structure has been successfully power tested to a gradient larger than 50 MV/m, well above the nominal level of 28 MV/m. The measured dark current and break down rates are well in the specifications.

TUPP112	Study of a C-Band TW Electron Gun for SwissFEL	686
SUPG032	use link to see paper's listing under its alternate paper code
	M. Schaer, A. Citterio, P. Craievich, L. Stingelin, R. Zennaro PSI, Villigen PSI, Switzerland
	For a future upgrade of the SwissFEL facility, the replacement of the S-band standing wave electron gun by a C-band standing wave, or traveling wave gun is investigated. The full model of the C-band TW gun is calculated with HFSS and is characterized by an almost vanishing group velocity in the first cell to increase the field at the cathode. ASTRA simulations predict that in the case of the C-band SW gun, a two times higher peak current of ~ 40 A can be generated while still preserving the low slice emittance of ~ 0.2 um at 200 pC, due to the higher electric field on cathode and improved magnetic focusing. This would help to halve the overall beam compression factor, relax the phase stability requirement of S- and X-band systems operated off-crest for compression and decrease the gain curve in theμbunch instability. Compared to the SW gun, a TW gun provides a more homogeneous acceleration and does not require any circulator. In this study, the preliminary RF design and beam performance of a C-band TW gun is presented and compared to a pure C-band SW gun presently under design at Paul Scherrer Institut and to the operating S-band SW gun.

THPP114	The SwissFEL RF Gun: Manufacturing and Proof of Precision by Field Profile Measurements	1117
	U. Ellenberger, H. Blumer, M. Kleeb, L. Paly, M. Probst Paul Scherrer Institute, Villigen PSI, Switzerland M. Bopp, A. Citterio, H. Fitze, J.-Y. Raguin, A. Scherer, L. Stingelin PSI, Villigen PSI, Switzerland
	The high brightness electron source for SwissFEL is an in-house built 2.6 cell normal-conducting RF gun which is scaled to the RF frequency of 2'998.8 MHz. The RF gun is capable of operating at 100 Hz repetition rate and produces electron bunches at the exit of the RF gun of an energy of 7 MeV. Key features of the RF gun are described and how they have been implemented in the manufacturing process. RF field measurements of the RF gun are presented to account for the mechanical precision reached after manufacturing. The RF gun has been thoroughly tested in the SwissFEL injector test facility.

Paper

Title

Page

C-Band Load Development for the High Power Test of the SwissFEL RF Pulse Compressor

329

A. Citterio, J. Stettler, R. Zennaro
PSI, Villigen PSI, Switzerland

The SwissFEL C-band Linac will have 26 RF modules, each one consisting of a solid-state modulator and a 50 MW klystron that feeds a pulse compressor and four two meters long accelerating structures. The pulse compressor is of the Barrel Open Cavity type (BOC). A first prototype was successfully produced and high-power tested, reaching for full power klystron operation a peak power of 300 MW. For testing this BOC at maximum RF power, a broadband load was designed and built, based on a ridge waveguide design and high permeability stainless steel. Based on the experience gained at CERN for CLIC X-band high power loads, the RF design of the load was optimized to ensure high losses for a quite large range of magnetic steels. Test pieces were realized in three different magnetic steels to choose the best suited material commercially available. This paper reports about the RF design, material study, production and impressive high power results of this C-band load.

MOPP119

Measurements and High Power Test of the First C-band Accelerating Structure for SwissFEL

333

R. Zennaro, J. Alex, A. Citterio, J.-Y. Raguin
PSI, Villigen PSI, Switzerland

The SwissFEL project is based on a 5.8 GeV C-band Linac which is composed of 10⁴ accelerating structures with a length of 2 m each. Due to the absence of dimple tuning no local frequency correction is possible and hence ultra-precise machining is required. The paper reports on both low level and high power RF test of the first nominal structure produced. The required mechanical precision has been reached and the structure has been successfully power tested to a gradient larger than 50 MV/m, well above the nominal level of 28 MV/m. The measured dark current and break down rates are well in the specifications.

TUPP112

Study of a C-Band TW Electron Gun for SwissFEL

686

SUPG032

use link to see paper's listing under its alternate paper code

M. Schaer, A. Citterio, P. Craievich, L. Stingelin, R. Zennaro
PSI, Villigen PSI, Switzerland

For a future upgrade of the SwissFEL facility, the replacement of the S-band standing wave electron gun by a C-band standing wave, or traveling wave gun is investigated. The full model of the C-band TW gun is calculated with HFSS and is characterized by an almost vanishing group velocity in the first cell to increase the field at the cathode. ASTRA simulations predict that in the case of the C-band SW gun, a two times higher peak current of ~ 40 A can be generated while still preserving the low slice emittance of ~ 0.2 um at 200 pC, due to the higher electric field on cathode and improved magnetic focusing. This would help to halve the overall beam compression factor, relax the phase stability requirement of S- and X-band systems operated off-crest for compression and decrease the gain curve in theμbunch instability. Compared to the SW gun, a TW gun provides a more homogeneous acceleration and does not require any circulator. In this study, the preliminary RF design and beam performance of a C-band TW gun is presented and compared to a pure C-band SW gun presently under design at Paul Scherrer Institut and to the operating S-band SW gun.

THPP114

The SwissFEL RF Gun: Manufacturing and Proof of Precision by Field Profile Measurements

1117

U. Ellenberger, H. Blumer, M. Kleeb, L. Paly, M. Probst
Paul Scherrer Institute, Villigen PSI, Switzerland
M. Bopp, A. Citterio, H. Fitze, J.-Y. Raguin, A. Scherer, L. Stingelin
PSI, Villigen PSI, Switzerland

The high brightness electron source for SwissFEL is an in-house built 2.6 cell normal-conducting RF gun which is scaled to the RF frequency of 2'998.8 MHz. The RF gun is capable of operating at 100 Hz repetition rate and produces electron bunches at the exit of the RF gun of an energy of 7 MeV. Key features of the RF gun are described and how they have been implemented in the manufacturing process. RF field measurements of the RF gun are presented to account for the mechanical precision reached after manufacturing. The RF gun has been thoroughly tested in the SwissFEL injector test facility.