Wish list for July May testbeam

1. Wish list for July May testbeam Keep It (Stupidly) Simple.. 1

2. Measurements, Mechanics, Monitoring mmm!!!

3. General considerations • Calibration – how is this done, does it change when we change thresholds • Propose to have same settings as last time • Ikrum increased to 10 • Preamp current increased: IF calibrations done this week (testpulse + results from alessandra) show that there is a gain • Rich set of measurements with only DUT and telescope • How do we calibrate/save files during testbeam • What is depletion voltage of sensor, what is limitation on bias voltage • Principal objective • Measure strip resolution as a function of angle • Measure 150 um thick resolution as a function of angle • We know we can do it! 3

4. Pixel-Pixel uniformity • Last testbeam: 1000 frames – 45000 tracks • 200 frames (possibly with a more focussed beam) would give a nice measurement • Should be compared with testpulse calibration

5. Resolution • Very important to have maximum stability through the measurement! • Making alignment files is a pain • We are at the micron level, so the calibration is very important – we can’t consider doing a scan unless we are sure that the testpulse curve is available • Want a full scan with 2d angles

6. Landau distributions, Gain(Track independent measurement) • Demonstrate satisfactory landau reconstruction • Total charge as function of cluster size • Fraction of charge in peak pixel, neighboring pixels • SNR as function of cluster size • Gain uniformity across timepix • Variation with preamp rise time? • Eventually track info contributes • Scan of ikrum ???!! Good statistics help! ~50000 tracks would be perfect Ikrum 40 Ikrum 5 6

7. Resolution • Main goal of this beam test • Imperative that we achieve the 4 um extrapolation precision of the telescope • As function of angle, bias voltage • Need enough tracks to make a good alignment • And enough tracks at each angle to measure • Bias voltage scan can be done at one angle only • Ideally aim for 10000 tracks per angle -20,-14,-10,-6,-2,0,2,6,10,14 40 um pitch illustration 7

8. Efficiency • Assume that timepix is >99.5% efficient, and we aim at a 0.1% measurement • 10000 tracks is safe for the device • A few more if we want to scan the surface or look between pixels (important for the 3d device) • Also need to scan efficiency as function of threshold • Factors affecting efficiency measurement: • 4 us to close timepix shutter • deadtime in telescope trigger • With intensities and acceptance comparable to last year we think that these factors will 8

9. Efficiency (cont) • Current scheme is to • read out 64 triggers • close the time pix (~ 4 us) • impose a dead time (e.g. 150 ms) • This gives 30 mini spills per spill (file handling issues?) • And roughly 500 tracks in timepix per spill • Efficiency measurement is affected by • tracks arriving during trigger dead time • tracks arriving during time pix closure • roughly: for very high efficiency and 2x10**6 particles per spill • these numbers give a “fake” efficiency of 0.4% • So for high efficiencies we are safe • But need higher statistics to measure the effect and remove the systematic error • Adding a scintillator would speed up things for timepix (but is it really necessary?)

10. Timewalk • Possible with telescope alone – should consider increasing threshold in ToA devices to increase number of 1 pixel clusters • Depends vitally on what calibration and lab measurements show us this week

11. Measurement Priorities? • Resolution as a function of angle • For strips • For 150 um pixels • ToA, for a preamp scan on DUT • Efficiency as a function of threshold • Voltage scan for both detectors

12. Other points • Setup a dedicated mailing list or use upgrade mailing list? • Electronic logbook would also be useful to record discussions and development (I am strongly in favour) • We already have some volunteers for shifts and a summer student.. should firm up on the manpower • (how many days will be have as main user?)