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

2. Simon Jolly, Imperial College2 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.

3. 24th January 2007Simon Jolly, Imperial College3 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…).

4. 24th January 2007Simon Jolly, Imperial College4 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. –20m x 20m pixels (twice as large as PCO). –Range of intensifier tubes. –VERY long delivery times on tubes (high demand from Hamamatsu).

5. 24th January 2007Simon Jolly, Imperial College5 PI-MAX Intensifier QE Curves Gen II Gen III filmless PCO

6. 24th January 2007Simon Jolly, Imperial College6 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.

7. 24th January 2007Simon Jolly, Imperial College7 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 >100s). 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…

8. 24th January 2007Simon Jolly, Imperial College8 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_1http://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?

9. 24th January 2007Simon Jolly, Imperial College9 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.