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Progress of Mk.II Pepperpot: Camera, Scintillator and Data Analysis

Progress of Mk.II Pepperpot: Camera, Scintillator and Data Analysis. Simon Jolly Imperial College 24 th January 2007. Mk.II Improvements Over Mk.I. Mechanical improvements (PJS). Larger scintillator/pepperpot screen for better coverage. Scintillator that survives…

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Progress of Mk.II Pepperpot: Camera, Scintillator and Data Analysis

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  1. Progress of Mk.II Pepperpot: Camera, Scintillator and Data Analysis Simon Jolly Imperial College 24th January 2007

  2. Mk.II Improvements Over Mk.I • Mechanical improvements (PJS). • Larger scintillator/pepperpot screen for better coverage. • Scintillator that survives… • Faster camera with lower noise floor. • Improve data analysis. Simon Jolly, Imperial College

  3. Improved Data Analysis • Previous method: average weighted pixel intensities from one spot to produce one point on emittance plot. • New method: use every pixel, ray-tracing from hole centre. • LOTS more data: 25 x 25 x 51 x 51 x 5 matrix (x, y, x’, y’, intensity, for every pixel at every hole location). Data analysis takes longer… • Emittance histogram “regeneration” should not be necessary for Mk.II; not yet tested on expanded Mk.I data (still some teething troubles…). Simon Jolly, Imperial College

  4. New Camera • Current camera (PCO 2000) has some problems: • Software unstable & limited (all data analysis in Matlab). • No signal amplification: need lots of light; can only integrate whole pulses. • Noise floor artifically set at 100 counts: no low light sensitivity. • A number of other things we were unaware of when purchasing camera… • With extra money, could we purchase a faster camera with MCP? • Best option looks like Princeton/PIActon PIMAX 1300: • <10ns gating. • 1340 x 1300 pixel resolution. • 20mm x 20mm pixels (twice as large as PCO). • Range of intensifier tubes. • VERY long delivery times on tubes (high demand from Hamamatsu). Simon Jolly, Imperial College

  5. PI-MAX Intensifier QE Curves Gen III filmless Gen II Gen III PCO Simon Jolly, Imperial College

  6. Intensifier Choices • Gen II gives broadest spectral response but much lower QE. • Gen III filmless is the opposite: narrow, but high QE. • Gen III gives better compromise, but longest delivery times (US Military buying them all…). • How quick do we need to order? • Measure scintillator first? Response looks similar to PCO, plus Ce-doped quartz peaks at 395nm. Simon Jolly, Imperial College

  7. New Scintillator • Quartz has given best results so far: • Virtually no degradation in light output. • Burn marks appear for pepperpot measurement, but don’t affect light intensity. • Too slow for sub-pulse measurements (decay time >100ms). • Looking for single 150mm x 150mm plate from several manufacturers. • Heraeus most promising: can provide undoped and Ce-doped screen. • Ce-doping should improve speed (80ns decay) and light output, but may affect radiation hardness… Simon Jolly, Imperial College

  8. Fast Scintillator • Quartz works for slow measurements (integrating single pulse), but not fast. • Ce-doped quartz screens from Heraeus used in previous GSI/Darmstadt experiment: • http://prola.aps.org/pdf/PRL/v85/i21/p4518_1 • However, doping may affect radiation hardness: doping sites make easy colour centres, reducing scintillation efficiency. • May need fast, undoped scintillator: with new camera, can survive with lower light output. How about Sapphire? Simon Jolly, Imperial College

  9. Alignment • Need better method to measure alignment/orientation and focal plane of scintillator. • Previously used rulers mounted on support: many drawbacks… • Using quartz/sapphire, can etch graticule on beam-side surface of glass. • Use 3 x 3 grid of 3mm squares in centre of plate: • Can now get orientation, scaling and focus. Simon Jolly, Imperial College

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