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July Test Beam Wish List: Keeping Measurements Simple and Effective

This document outlines key considerations and priorities for the upcoming July test beam. Emphasis is placed on ensuring calibration protocols are consistent with previous tests, particularly as we increase Ikrum and preamp current settings. Critical measurements to be performed include strip resolution as a function of angle, pixel uniformity, and efficiency assessments. We aim for robust statistical data with at least 50,000 tracks across various angles while ensuring high stability and alignment precision. Additional points include the need for an electronic logbook and organized volunteer shifts.

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July Test Beam Wish List: Keeping Measurements Simple and Effective

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  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?)

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