PREX/CREX Feb 7, 2018 10:00am

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  1. PMT linearity studies: Devi docDB
    • DeA: filter wheel goes to 1% not 0 (in slide 2 bullet 3)
    • KP: what are the spikes in the pair asymmetry DeA: this is related to filter 1. (slide 5, fig 1)
    • KP: why are the asymmetries double peaked? DeA: from higher light levels we get two peaks. SR: you could change the function generator to see if this goes away. KP: these could be always there and we could only see it when the light levels are higher. DM: will investigate. KK: take a run where you got to 50 Hz.
    • KK: what is the sensitivity for the linearity? DM: we are seeing about 0.2% (this particular plots is 0.1%)
    • KK: what does positive non linearity slope mean? KP: anti-saturation!? meaning that you get higher gain than you expect for the HV you are at. KK: we should think about what these mean carefully. We need to figure out how we assign systematic error. It could be something related to the preAmplifier.
    • DeA: we expect few nA for PREX and ~0.3 nA for CREX. SR: how do get these currents? DA: we use a unit gain PMT base for calibration
    • KP: could we have a slide explanation on how we get light levels and photocathode current? DA: will put something together
    • DM: PMT2 looks worse because we can’t reach the 0 crossing for 10nA. KK: we should be lower than 15nA always and we have to design the preAmp to make sure we get what we need.
    • KP: in Qweak we had variations in the signal level with the raster on the level of ~30%. Would this matter for us? KK: we should remember this point and worry about it during the run. KP: it would great to have a flat linearity for factors of two from where we decide to run. KK: we could run a fact MC for this problem.
    • KP & DM: we should have an in-situ system for PREX/CREX
  2. Dump O ring: Adam haplog3472
    • AZ: looking at o-ring connection between the hall and dump beam pipes
    • AZ: we simulated a larger o-ring to get enough statistics.
    • KP: looking where the shower source (att 11) (except the o-ring cutout) we can see a lot of soft photons, but most of the energy deposited is from e-
    • KP: the energy deposited is a better metric than NEIL. the cern document shows that at 5.5e5 the o-ring is destroyed. SR: how is failure defined? KP: compression set relates to failure: at these rad levels they claim losing about 20% of the compression means vacuum problems.
    • KP: it looks ok from this calculation but we need to investigate further.
  3. FLUKA simulations: Victoria docDB
    • KP: top view looking at one point as a function of time.
    • KP: these plots will be needed to guide the deinstallation.
    • KP: the levels are somewhat smaller than expected, but they look really encouraging
    • DA: we will look at CREX as well and see what levels we have from the combined runs
  4. draft schedule for the collaboration meeting: Seamus
    • SR: take a look to make sure you are ok with your speaking time
    • SR: register for the meeting


Kent P, Dave G, Ciprian G, Adam Z, Amali P, Chandan G, David A, Dustin M, Paul S, Ryan R, Silviu D, Tyler K, Seamus R, Devi A, Sanghwa P, KK, Caryn P, Tao Y, Jay B, Juliette M,


Victoria O,