Broadband Single-Shot Electron Spectrometer for GeV-Class Laser Plasma Based Accelerators

Laser-plasma-based accelerators can provide electrons over a broad energy range and/or with large momentum spread. The electron beam energy distribution can be controlled via accurate control of laser and plasma properties, and beams with energies ranging from'0.5 to 1000 MeV have been observed. Measuring these energy distributions in a single shot requires the use of a diagnostic with large momentum acceptance and, ideally, sufficient resolution to accurately measure energy spread in the case of narrow energy spread. Such a broadband single-shot electron magnetic spectrometer for GeV-class laser-plasma-based accelerators has been developed at Lawrence Berkeley National Laboratory. A detailed description of the hardware and the design concept is presented, as well as a performance evaluation of the spectrometer. The spectrometer covered electron beam energies raging from 0.01 to 1.1 GeV in a single shot, and enabled the simultaneous measurement of the laser properties at the exit of the accelerator through the use of a sufficiently large pole gap. Based on measured field maps and 3rd-order transport analysis, a few percent-level resolution and determination of the absolute energy were achieved over the entire energy range. Laser-plasma-based accelerator experiments demonstrated the capability of the spectrometer as a diagnostic and its suitability for such a broadband electron source

The KamLAND Full-Volume Calibration System

We have successfully built and operated a source deployment system for the KamLAND detector. This system was used to position radioactive sources throughout the delicate 1-kton liquid scintillator volume, while meeting stringent material cleanliness, material compatibility, and safety requirements. The calibration data obtained with this device were used to fully characterize detector position and energy reconstruction biases. As a result, the uncertainty in the size of the detector fiducial volume was reduced by a factor of two. Prior to calibration with this system, the fiducial volume was the largest source of systematic uncertainty in measuring the number of anti-neutrinos detected by KamLAND. This paper describes the design, operation and performance of this unique calibration system.Comment: 30 pages, 22 figures, to be submitted to JINS

Ion Source and Injector Improvements at the SuperHILAC

Major improvements have been made on the Adam injector at the SuperHILAC heavy ion accelerator. Adam is a pressurized Cockcroft-Walton injector, typically run at voltages in excess of 2 MeV. The PIG ion source was redesigned to increase the length of the discharge column and the extraction slit, while remaining within the magnet poles of the source magnet. To maintain cooling, part of the thinner soft-iron end cap was replaced with a copper section, modifying the magnetic circuit. These modifications resulted in more than doubling the ion beam intensity. A large liquid nitrogen cryotrap within the pressure vessel was replaced by an RF shielded, commercial cryopump head with a custom pumping array. This reduced the pressure at the ground end of the injector by an order of magnitude and reduced that at the source by a factor of two, even with the additional gas load due to the longer slit. The pressure reduction was essential to minimize charge exchange loss of the highly charged ions, such as Fe{sup 4+}. Plans are underway to replace a 3 watt cryopump in the terminal end with a 10 watt pump which is expected to result in a 50% faster cooldown time, and greater than a 50% increase in running time before regeneration of the cryopump is necessary. 3 refs., 4 figs

Broadband Single-Shot Electron Spectrometer for GeV-Class Laser Plasma Based Accelerators

Abstract Laser-plasma-based accelerators can provide electrons over a broad energy range and/or with large momentum spread. The electron beam energy distribution can be controlled via accurate control of laser and plasma properties, and beams with energies ranging from 0.5 to 1000 MeV have been observed. Measuring these energy distributions in a single shot requires the use of a diagnostic with large momentum acceptance and, ideally, sufficient resolution to accurately measure energy spread in the case of narrow energy spread. Such a broadband single-shot electron magnetic spectrometer for GeV-class laser-plasma-based accelerators has been developed at Lawrence Berkeley National Laboratory. A detailed description of the hardware and the design concept is presented, as well as a performance evaluation of the spectrometer. The spectrometer covered electron beam energies raging from 0.01 to 1.1 GeV in a single shot, and enabled the simultaneous measurement of the laser properties at the exit of the accelerator through the use of a sufficiently large pole gap. Based on measured field maps and 3rd-order transport analysis, a few percent-level resolution and determination of the absolute energy were achieved over the entire energy range. Laser-plasma-based accelerator experiments demonstrated the capability of the spectrometer as a diagnostic and its suitability for such a broadband electron source

An Approach towards a Long-life, Microwave-assisted H - Ion Source for Proton Drivers

Abstract. This paper reports on experiments aimed at developing a new high-intensity H -ion source with long lifetime whose concept had recently been introduced. Starting from the motivation for this effort, several steps of the earlier development work are recapitulated, and the performance of the latest design variant is discussed in detail. The basic concept consists in coupling an ECR ion source to a standard SNS multi-cusp H -ion source that is driven by pulsed dc, rather than rf, power. As a key result, an electron beam of 1.5 A current has been extracted from the ECR discharge operating at 1.9 kW c. w. power, and a maximum discharge current of 17.5 A was achieved in the H -ion source. Production of H -ions, however could not yet been demonstrated in the one, preliminary, experiment conducted so far. The paper concludes by outlining further envisaged development steps for the plasma generator and an expansion towards a novel extraction system

An Approach towards a Long-life, Microwave-assisted H- Ion Soucre for Proton Drivers

This paper reports on experiments aimed at developing a new high-intensity H{sup -} ion source with long lifetime whose concept had recently been introduced. Starting from the motivation for this effort, several steps of the earlier development work are recapitulated, and the performance of the latest design variant is discussed in detail. The basic concept consists in coupling an ECR ion source to a standard SNS multi-cusp H{sup -} ion source that is driven by pulsed dc, rather than rf, power. As a key result, an electron beam of 1.5 A current has been extracted from the ECR discharge operating at 1.9 kW c. w. power, and a maximum discharge current of 17.5 A was achieved in the H{sup -} ion source. Production of H{sup -} ions, however could not yet been demonstrated in the one, preliminary, experiment conducted so far. The paper concludes by outlining further envisaged development steps for the plasma generator and an expansion towards a novel extraction system