FEL2014 - List of Keywords (collimation)

Paper	Title	Other Keywords	Page
THP031	Further Understanding the LCLS Injector Emittance	emittance, electron, laser, radiation	774
	F. Zhou, K.L.F. Bane, Y. Ding, Z. Huang, H. Loos SLAC, Menlo Park, California, USA
	Funding: US DOE under contract No. DE-AC02-76SF00515 Notable COTR effect from the LCLS laser heater chicane is recently observed at the LCLS injector OTR screen, used for routine emittance measurements. The emittance with the OTR screen is under-estimated by about 30% compared to the values with the wire scanner located next to the OTR screen. The emittance with the OTR and wire scanner is compared and relevant analyses are presented. Slice emittance upstream of the LCLS BC1 is measured using a traditional transverse cavity. Recently, slice emittance downstream of the BC1 is able to be measured with a newly developed technique, using a collimator located in the middle of the BC1. The parasitic effects of using the collimator for slice emittance measurement are evaluated. The slice emittance before and after the BC1 is compared. The dependence of the slice emittance on the linearizer’s transverse offset and CSR effect from the BC1 is discussed.

THP041	Development of All-metal Stacked-double Gate Field Emitter Array Cathodes for X-ray Free-electron Laser Applications	electron, emittance, laser, resonance	811
	S. Tsujino, H.-H. Braun, P. Das Kanungo, V. Guzenko, C. Lee, Y. Oh, M. Paraliev PSI, Villigen PSI, Switzerland T. Feurer Universität Bern, Institute of Applied Physics, Bern, Switzerland
	Funding: This work was partially supported by the Swiss National Science Foundation Nos. 200020₁43428 and 2000021₁47101. We report the design, fabrication, and characterization of all-metal stacked-double-gate field emitter array (FEA) cathodes as a potential upgrade option of SwissFEL cathode at the Paul Scherrer Institute. Single-gate FEAs have demonstrated stable operation and gated field emission in pulsed diode gun with gradient up to 30 MV/m with pulse duration down to 200 ps and generation of 5 pC electron bunches by near infrared laser-induced field emission. However for high brightness applications it is crucial to reduce the beam divergence of individual beamlet by a suitable double-gate structure. The challenge lies in suppressing the concomitant decrease of the emission current when a negative focusing potential is applied to the second gate. To solve this problem, a stacked-double-gate FEAs with large collimation gate aperture diameter has been proposed. The intrinsic transverse emittance evaluated from a beam measurement for 1 mm-diameter FEA was below 0.1 mm-mrad. Compatibility with neon-gas conditioning to improve the beam uniformity and high emission current with double-gate FEAs were also demonstrated recently. The current research is focusing on the combination of the surface-plasmon-polariton resonance of the gate electrode and the near infrared laser-induced field emission to realize an ultrafast and ultrabright FEA cathode.

Paper

Title

Other Keywords

Page

THP031

Further Understanding the LCLS Injector Emittance

emittance, electron, laser, radiation

774

F. Zhou, K.L.F. Bane, Y. Ding, Z. Huang, H. Loos
SLAC, Menlo Park, California, USA

Funding: US DOE under contract No. DE-AC02-76SF00515
Notable COTR effect from the LCLS laser heater chicane is recently observed at the LCLS injector OTR screen, used for routine emittance measurements. The emittance with the OTR screen is under-estimated by about 30% compared to the values with the wire scanner located next to the OTR screen. The emittance with the OTR and wire scanner is compared and relevant analyses are presented. Slice emittance upstream of the LCLS BC1 is measured using a traditional transverse cavity. Recently, slice emittance downstream of the BC1 is able to be measured with a newly developed technique, using a collimator located in the middle of the BC1. The parasitic effects of using the collimator for slice emittance measurement are evaluated. The slice emittance before and after the BC1 is compared. The dependence of the slice emittance on the linearizer’s transverse offset and CSR effect from the BC1 is discussed.

THP041

Development of All-metal Stacked-double Gate Field Emitter Array Cathodes for X-ray Free-electron Laser Applications

electron, emittance, laser, resonance

811

S. Tsujino, H.-H. Braun, P. Das Kanungo, V. Guzenko, C. Lee, Y. Oh, M. Paraliev
PSI, Villigen PSI, Switzerland
T. Feurer
Universität Bern, Institute of Applied Physics, Bern, Switzerland

Funding: This work was partially supported by the Swiss National Science Foundation Nos. 200020₁43428 and 2000021₁47101.
We report the design, fabrication, and characterization of all-metal stacked-double-gate field emitter array (FEA) cathodes as a potential upgrade option of SwissFEL cathode at the Paul Scherrer Institute. Single-gate FEAs have demonstrated stable operation and gated field emission in pulsed diode gun with gradient up to 30 MV/m with pulse duration down to 200 ps and generation of 5 pC electron bunches by near infrared laser-induced field emission. However for high brightness applications it is crucial to reduce the beam divergence of individual beamlet by a suitable double-gate structure. The challenge lies in suppressing the concomitant decrease of the emission current when a negative focusing potential is applied to the second gate. To solve this problem, a stacked-double-gate FEAs with large collimation gate aperture diameter has been proposed. The intrinsic transverse emittance evaluated from a beam measurement for 1 mm-diameter FEA was below 0.1 mm-mrad. Compatibility with neon-gas conditioning to improve the beam uniformity and high emission current with double-gate FEAs were also demonstrated recently. The current research is focusing on the combination of the surface-plasmon-polariton resonance of the gate electrode and the near infrared laser-induced field emission to realize an ultrafast and ultrabright FEA cathode.