Status of the ALICE Energy Recovery Linac

Jones, L. B.; Jamison, S. P.; Saveliev, Yuri; Middleman, Keith; Smith, S. L.

doi:10.1063/1.3215597

Cited by 7 publications

(5 citation statements)

References 6 publications

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“…The Jefferson Lab Free Electron Laser employed the first photogun to operate at significantly higher voltage, $320 kV [11]. Today a number of photoguns operate at comparable values albeit still lower voltage than desired [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

BastaniNejad

Mohamed

Elmustafa

et al. 2012

Phys. Rev. ST Accel. Beams

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The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirrorlike finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV=m.

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Section: Introductionmentioning

confidence: 99%

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

BastaniNejad

Mohamed

Elmustafa

et al. 2012

Phys. Rev. ST Accel. Beams

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“…Fieldemitted electrons from the support-rod electrode may cause damage to the ceramic insulator. [10][11][12] As a result, stable operation of such electron guns at 500 kV has not yet been achieved in spite of the intensive gun development efforts in the world.…”

Section: Introductionmentioning

confidence: 98%

“…9 Such electron guns are under development for future ERLs in many laboratories. [10][11][12][13] The goals of these gun development programs are average current of 10-100 mA and normalized emittance of 0.1-1 mm mrad. To suppress emittance growth by space charge effect, the gun voltage must be 500 kV or higher.…”

Section: Introductionmentioning

confidence: 99%

High-voltage testing of a 500-kV dc photocathode electron gun

Nagai

Hajima

Nishimori

et al. 2010

Review of Scientific Instruments

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A high-voltage dc photocathode electron gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 h was demonstrated at an acceleration voltage of 500 kV. The dc photocathode electron gun is designed for future light sources based on energy-recovery linac and consists of a Cockcroft-Walton generator, a segmented cylindrical ceramic insulator, guard-ring electrodes, a support-rod electrode, a vacuum chamber, and a pressurized insulating gas tank. The segmented cylindrical ceramic insulator and the guard-ring electrodes were utilized to prevent any damage to the insulator from electrons emitted by the support-rod electrode.

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“…For these reasons, the onset of field emission determines the acceptable operating voltage of the photogun, often restricting operation to voltages significantly below the desired value required for optimized electron beam parameters. This is especially true for today's photoelectron gun projects aimed at operating at 350 kV direct current (DC) and higher, [1][2][3][4][5][6] where eliminating field emission is one of the key technological challenges.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns

BastaniNejad

Elmustafa

Forman

et al. 2015

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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DC high voltage photoelectron guns are used to produce polarized electron beams for accelerator-based nuclear and high-energy physics research. Low-level field emission (∼nA) from the cathode electrode degrades the vacuum within the photogun and reduces the photoelectron yield of the delicate GaAs-based photocathode used to produce the electron beams. High-level field emission (>μA) can cause significant damage the photogun. To minimize field emission, stainless steel electrodes are typically diamond-paste polished, a labor-intensive process often yielding field emission performance with a high degree of variability, sample to sample. As an alternative approach and as comparative study, the performance of electrodes electropolished by conventional commercially available methods is presented. Our observations indicate the electropolished electrodes exhibited less field emission upon the initial application of high voltage, but showed less improvement with gas conditioning compared to the diamond-paste polished electrodes. In contrast, the diamond-paste polished electrodes responded favorably to gas conditioning, and ultimately reached higher voltages and field strengths without field emission, compared to electrodes that were only electropolished. The best performing electrode was one that was both diamond-paste polished and electropolished, reaching a field strength of 18.7 MV/m while generating less than 100 pA of field emission. The authors speculate that the combined processes were the most effective at reducing both large and small scale topography. However, surface science evaluation indicates topography cannot be the only relevant parameter when it comes to predicting field emission performance.

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Status of the ALICE Energy Recovery Linac

Cited by 7 publications

References 6 publications

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

High-voltage testing of a 500-kV dc photocathode electron gun

Evaluation of electropolished stainless steel electrodes for use in DC high voltage photoelectron guns

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