FEL2009 - List of Authors (O'Shea, P.G.)

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O'Shea, P.G.

Paper	Title	Page
TUPC52	Towards A Multialkali Dispenser Photocathode: Experiment and Theory	364
	E.J. Montgomery, D.W. Feldman, P.G. O'Shea, P.Z. Pan, N. Sennett, C. Stortstrom UMD, College Park, Maryland K. L. Jensen NRL, Washington, DC
	High performance FELs demand photocathodes with high quantum efficiencies (QE), kHr life, kA/cm² peak and A/cm² average current, and ps response. In harsh accelerator vacuum conditions, having delicate cesium-based coatings, efficient photocathodes face shortened life. The UMD dispenser photocathode extends lifetime by resupplying cesium from a subsurface reservoir through a porous substrate [1], and recesiation can rejuvenate cesiated cathodes (Cs:Ag) after contamination [2]. These studies have validated theory that can presently treat both coated metals and semiconductors [3, 4]. Other alkali metals (Na, K) may also be deposited singly or together for better QE (e.g., Cs2KSb and other high QE multi-alkalis). Towards that end and to refine theory, we here report fabrication and testing of K:Ag and Na:Ag complementing the previously cited Cs:Ag work. Models of coating-dependent QE analyze the K and Na data on metal (e.g., silver) polycrystalline surfaces. The status of an effort to incorporate these models into PIC beam simulation codes such as MICHELLE [5] shall also be indicated. [1] Moody et al, APL 90,114108(2007) [2] Montgomery et al, AIP Proc. 1086, 599(2009) [3] Jensen et al, JAP104, 044907(2008) [4] Jensen et al, JAP102, 074902(2007) [5] Jensen et al, JVSTB26(2), 831(2008)

Paper

Title

Page

TUPC52

Towards A Multialkali Dispenser Photocathode: Experiment and Theory

364

E.J. Montgomery, D.W. Feldman, P.G. O'Shea, P.Z. Pan, N. Sennett, C. Stortstrom
UMD, College Park, Maryland
K. L. Jensen
NRL, Washington, DC

High performance FELs demand photocathodes with high quantum efficiencies (QE), kHr life, kA/cm² peak and A/cm² average current, and ps response. In harsh accelerator vacuum conditions, having delicate cesium-based coatings, efficient photocathodes face shortened life. The UMD dispenser photocathode extends lifetime by resupplying cesium from a subsurface reservoir through a porous substrate [1], and recesiation can rejuvenate cesiated cathodes (Cs:Ag) after contamination [2]. These studies have validated theory that can presently treat both coated metals and semiconductors [3, 4]. Other alkali metals (Na, K) may also be deposited singly or together for better QE (e.g., Cs2KSb and other high QE multi-alkalis). Towards that end and to refine theory, we here report fabrication and testing of K:Ag and Na:Ag complementing the previously cited Cs:Ag work. Models of coating-dependent QE analyze the K and Na data on metal (e.g., silver) polycrystalline surfaces. The status of an effort to incorporate these models into PIC beam simulation codes such as MICHELLE [5] shall also be indicated.

[1] Moody et al, APL 90,114108(2007)
[2] Montgomery et al, AIP Proc. 1086, 599(2009)
[3] Jensen et al, JAP104, 044907(2008)
[4] Jensen et al, JAP102, 074902(2007)
[5] Jensen et al, JVSTB26(2), 831(2008)