2011 Particle Accelerator Conference - List of Authors (Mammei, R.R.)

Paper	Title	Page
WEP284	Performance Study of K2CsSb Photocathode inside a DC High Voltage Gun	2017
	T. Rao, J. Smedley BNL, Upton, Long Island, New York, USA J.M. Grames, R.R. Mammei, J.L. McCarter, M. Poelker, R. Suleiman JLAB, Newport News, Virginia, USA
	Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grant DE-FG02-08ER41547. In the past decade, there has been considerable interest in the generation of tens of mA average current in a photoinjector. Until recently, GaAs:Cs cathodes and K2CsSb cathodes have been tested successfully in DC and RF injectors respectively for this application. Our goal is to test the GaAs:Cs in RF injector and the K2CsSb cathode in the DC gun in order to widen our choices. Since the multialkali cathode is a compound with uniform stochiometry over its entire thickness, we anticipate that the life time issues seen in GaAs:Cs due surface damage by ion bombardment would be minimized with this material. Hence successful operation of the K2CsSb cathode in DC gun could lead to a relatively robust electron source capable of delivering ampere level currents. In order to test the performance of K2CsSb cathode in a DC gun, we have designed and built a load lock system that would allow the fabrication of the cathode at BNL and its testing at JLab. In this paper, we will present the design of the load-lock system, cathode fabrication, and the cathode performance in the preparation chamber and in the DC gun.

WEP287	Field Emission Measurements from Niobium Electrodes	2020
	M. BastaniNejad Old Dominion University, Norfolk, Virginia, USA P.A. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, R.R. Mammei, M. Poelker JLAB, Newport News, Virginia, USA
	Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and/or ion bombardment and high levels of field emission can damage the ceramic insulator. Niobium electrodes (single crystal, large grain and fine grain) were characterized using a DC high voltage field emission test stand at maximum voltage -225kV and electric field gradient > 10MV/m. Niobium electrodes appear to be superior to diamond-paste polished stainless steel electrodes.

Paper

Title

Page

Performance Study of K2CsSb Photocathode inside a DC High Voltage Gun

2017

T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA
J.M. Grames, R.R. Mammei, J.L. McCarter, M. Poelker, R. Suleiman
JLAB, Newport News, Virginia, USA

Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grant DE-FG02-08ER41547.
In the past decade, there has been considerable interest in the generation of tens of mA average current in a photoinjector. Until recently, GaAs:Cs cathodes and K2CsSb cathodes have been tested successfully in DC and RF injectors respectively for this application. Our goal is to test the GaAs:Cs in RF injector and the K2CsSb cathode in the DC gun in order to widen our choices. Since the multialkali cathode is a compound with uniform stochiometry over its entire thickness, we anticipate that the life time issues seen in GaAs:Cs due surface damage by ion bombardment would be minimized with this material. Hence successful operation of the K2CsSb cathode in DC gun could lead to a relatively robust electron source capable of delivering ampere level currents. In order to test the performance of K2CsSb cathode in a DC gun, we have designed and built a load lock system that would allow the fabrication of the cathode at BNL and its testing at JLab. In this paper, we will present the design of the load-lock system, cathode fabrication, and the cathode performance in the preparation chamber and in the DC gun.

WEP287

Field Emission Measurements from Niobium Electrodes

2020

M. BastaniNejad
Old Dominion University, Norfolk, Virginia, USA
P.A. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, R.R. Mammei, M. Poelker
JLAB, Newport News, Virginia, USA

Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and/or ion bombardment and high levels of field emission can damage the ceramic insulator. Niobium electrodes (single crystal, large grain and fine grain) were characterized using a DC high voltage field emission test stand at maximum voltage -225kV and electric field gradient > 10MV/m. Niobium electrodes appear to be superior to diamond-paste polished stainless steel electrodes.