PAC2013 - List of Authors (Stockli, M.P.)

Paper	Title	Page
TUPSM22	Improving Efficiency of Ions Production in Ion Source with Saddle Antenna	682
	V.G. Dudnikov, R.P. Johnson Muons, Inc, Illinois, USA T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton ORNL, Oak Ridge, Tennessee, USA M.W. Turvey University of Florida, Gainesville, Florida, USA
	Funding: Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690. Extraction of negative ions from RF surface plasma source (SPS) with saddle antenna radio frequency (SA RF) discharge is considered. Several versions of new plasma generators with different antennas and magnetic field configurations were tested in the SNS small Test Stand. The efficiency of positive ion generation in plasma has been improved up to ~90 mA/cm² per 1 kW of RF power at 13.56 MHz. For first cesiation was used a heating of the cesium chromate cartridges by CW RF discharge. A small oven for cesium compounds and alloys decomposition by heating was developed and tested. After cesiation a current of negative ions to the collector was increased from 0.5 mA to 10 mA with RF power ~ 1.5 kW in the plasma and longitudinal magnetic field Bl~250 Gauss. With increase of a longitudinal magnetic field the collector current can be increased up to 7 times. A stable long time generation of H⁻ beam without degradation was demonstrated in RF discharge with AlN discharge chamber.

FRYBB2	Development and Operation of the SNS Fast Chopper Systems	1473
	R.B. Saethre ORNL RAD, Oak Ridge, Tennessee, USA D.E. Anderson, C. Deibele, V.V. Peplov, M.P. Stockli ORNL, Oak Ridge, Tennessee, USA
	The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory requires fast chopper systems to create a series of mini-pulses in the Linear Accelerator (LINAC) for injection into the accumulation ring. The fast chopper systems are in the front end of the accelerator with one set of four choppers in the Low Energy Beam Transport (LEBT), immediately upstream of the Radio Frequency Quadrupole (RFQ), and another set of two choppers in the Medium Energy Beam Transport (MEBT), downstream of the RFQ, where the beam energy is approximately 2.5 MeV. Clean bunching requires fast rise and fall time and low jitter to minimize the amount of charge in the ring extraction gap. The chopper systems operate at a burst frequency of 1 MHz and a burst width of greater than 1 ms. The choppers have had historically poor reliability especially in the LEBT system. This paper describes the development of reliable LEBT and MEBT choppers and the operational performance since SNS commissioning in 2006.

Paper

Title

Page

Improving Efficiency of Ions Production in Ion Source with Saddle Antenna

682

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Illinois, USA
T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA
M.W. Turvey
University of Florida, Gainesville, Florida, USA

Funding: Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690.
Extraction of negative ions from RF surface plasma source (SPS) with saddle antenna radio frequency (SA RF) discharge is considered. Several versions of new plasma generators with different antennas and magnetic field configurations were tested in the SNS small Test Stand. The efficiency of positive ion generation in plasma has been improved up to ~90 mA/cm² per 1 kW of RF power at 13.56 MHz. For first cesiation was used a heating of the cesium chromate cartridges by CW RF discharge. A small oven for cesium compounds and alloys decomposition by heating was developed and tested. After cesiation a current of negative ions to the collector was increased from 0.5 mA to 10 mA with RF power ~ 1.5 kW in the plasma and longitudinal magnetic field Bl~250 Gauss. With increase of a longitudinal magnetic field the collector current can be increased up to 7 times. A stable long time generation of H⁻ beam without degradation was demonstrated in RF discharge with AlN discharge chamber.

FRYBB2

Development and Operation of the SNS Fast Chopper Systems

1473

R.B. Saethre
ORNL RAD, Oak Ridge, Tennessee, USA
D.E. Anderson, C. Deibele, V.V. Peplov, M.P. Stockli
ORNL, Oak Ridge, Tennessee, USA

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory requires fast chopper systems to create a series of mini-pulses in the Linear Accelerator (LINAC) for injection into the accumulation ring. The fast chopper systems are in the front end of the accelerator with one set of four choppers in the Low Energy Beam Transport (LEBT), immediately upstream of the Radio Frequency Quadrupole (RFQ), and another set of two choppers in the Medium Energy Beam Transport (MEBT), downstream of the RFQ, where the beam energy is approximately 2.5 MeV. Clean bunching requires fast rise and fall time and low jitter to minimize the amount of charge in the ring extraction gap. The chopper systems operate at a burst frequency of 1 MHz and a burst width of greater than 1 ms. The choppers have had historically poor reliability especially in the LEBT system. This paper describes the development of reliable LEBT and MEBT choppers and the operational performance since SNS commissioning in 2006.