# ITOP carrier amplifier test at Indiana University G. Visser 4/27/2015 (latest update) I use the recently (here) characterized JT0947 ch3 as input source.

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iTOP carrier amplifier test at Indiana University G. Visser 4/27/2015 (latest update) I use the recently (here) characterized JT0947 ch3 as input source for this work. At 3110V, mean gain is measured 3.64×10 5.

3010 V

As before we use this (800MHz analog BWL) for the gain measurement work. 3010 V

JT0947/ch3 3010 V direct, no amp Pedestal σ = 0.02332 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.072 to 0.70 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 12372.9 +/- 2999 p = 0.94528 +/- 0.07329 q = 1.24050 +/- 0.04934 c = 0.0901407 +/- 0.00088  137640 events in signal ( 6.3% ) [We expected 2200000 −12612(cut) −2062040(pedestal fit) = 125348 events in signal. Reasonable.]  mean signal size 0.197 Melectrons

Same plot except on linear scale JT0947/ch3 3010 V direct, no amp

JT0947/ch3 3110 V direct, no amp Pedestal σ = 0.025083 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.082 to 1.47 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 1220.41 +/- 44.58 p = 0.36669 +/- 0.01891 q = 1.70531 +/- 0.03849 c = 0.78737 +/- 0.02436  139592 events in signal ( 6.3% ) [We expected 2200000 −18190(cut) −2049780(pedestal fit) = 132030 events in signal. Reasonable.]  mean signal size 0.364 Melectrons

Same plot except on linear scale JT0947/ch3 3110 V direct, no amp

JT0947/ch3 3210 V direct, no amp Pedestal σ = 0.02805 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.11 to 2.36 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 1220.41 +/- 44.58 p = 0.36669 +/- 0.01891 q = 1.70531 +/- 0.03849 c = 0.78737 +/- 0.02436  139034 events in signal ( 6.3% ) [We expected 2200000 −22086(cut) −2042780(pedestal fit) = 135134 events in signal. Good.]  mean signal size 0.664 Melectrons

Same plot except on linear scale JT0947/ch3 3210 V direct, no amp

For example, the JT0947 ch3 3010V data above, was taken with the scope set for 1.2mV/div. At that setting, input-referred current noise is 53 pA/sqrt(Hz). So, with a 9 ns integration gate we expect to have pedestal rms of 22.2 k electrons. This compares well with the fitted pedestal rms 23.3 k electrons. We want to use same method to check the amplifier input-referred noise in different configurations. From SPICE for the amplifier in so-called “1x” configuration, the input-referred noise is 48 pA/sqrt(Hz), and in “4x” configuration (baseline for carrier rev E2/3) the input-referred noise is 26 pA/sqrt(Hz). So perhaps optimistically we expect pedestal rms of 20.1 k electrons and 10.9 k electrons, respectively.

20 events, with “1x” amplifier configuration

JT0947/ch3 3010 V Amp “1x” Other than signal polarity flip, the min & max voltage versus charge histogram looks about the same as before. We make cuts similar to before, to eliminate saturated events and some two-photon events. It is necessary to be careful that cuts (or saturation, if not cut!) don’t bias the upper end of the charge spectrum too much. Judgement is needed, inspect charge histogram w/ & w/out cuts.

JT0947/ch3 3010 V Amp “1x” Red: raw charge histogram Blue: charge historgam after cuts

JT0947/ch3 3010 V Amp “1x” Pedestal σ = 0.02130 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.064 to 0.64 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 14460.1 +/- 3374 p = 0.90774 +/- 0.06894 q = 1.27845 +/- 0.04929 c = 0.07701 +/- 0.0008367  135619 events in signal ( 6.2% ) [We expected 2200000 −2899(cut) −2073110(pedestal fit) = 123991 events in signal. Reasonable.]  mean signal size 0.175 Melectrons We assume the amplifier gain from SPICE: 3067 Ω. 11% low from expected result. Reason understood (see next slides). SPICE: Expected 0.0201 Melectrons.

Same plot except on linear scale JT0947/ch3 3010 V Amp “1x”

JT0947/ch3 3110 V Amp “1x” Pedestal σ = 0.02145 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.07 to 1.3 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 3762.15 +/- 325.9 p = 0.61477 +/- 0.03078 q = 1.40095 +/- 0.03595 c = 0.20195 +/- 0.00266  140482 events in signal ( 6.4% ) [We expected 2200000 −4320(cut) −2060310(pedestal fit) = 135370 events in signal. Reasonable.]  mean signal size 0.326 Melectrons We assume the amplifier gain from SPICE: 3067 Ω. 10% low from expected result. Reason understood (see next slides). SPICE: Expected 0.0201 Melectrons.

Same plot except on linear scale JT0947/ch3 3110 V Amp “1x”

Conclusions so far: Signals with amplifier, read through scope at IU, make sense in same analysis framework. (Of course, this is already known from IRSX work.) Pedestal rms corresponds very well with expected value from measured scope noise or from amplifier SPICE noise. “1x” amplifier gain looks ~10% lower than SPICE. In part this may be resistor tolerance, in part perhaps an effect of bandwidth limitation or AC coupling, or some charge lost due to nonlinear effects? Not clear. Next up: “4x” case. Hopefully it will be similarly 10% lower than SPICE, although IRSX results suggest it will be a further 22% lower.  The 10% discrepancy is explained: prototype circuit didn’t exactly match carrier rev E / SPICE circuit. Was effectively a 100 Ω / 1 kΩ voltage divider at the input, owing to bias resistor connection. Changed this now to match carrier rev E circuit, and replaced the R-C network capacitor w/ 5 pF (just in case that was not it’s value before) and the R with 49.9 Ω (it was for some reason 100 Ω). Following work uses this corrected amplifier circuit.

Minor notes (ignore this page): run 8: corrected amplifier (should have 3067 Ohm gain) run 9: changed to “4x” plan (34.8->69.8, 40.2->20) run 10: same but at 3010 V run 11: Wanted to understand pulse shape out of amplifier more certainly. Removed LMH6559, replaced it with 909 Ohm resistor. So output is now 20.18× attenuation not 2 × attenuation. (50 Ohm output R is also still in there, not touched!) Look at pulse shape, as well as comparing gain results run 11 – run 9. in all of these cases, scope is set with the proper attenuation factor. (Except, in LMH6559 case, we assume unity gain not the actual gain which may be ~1% lower.)

JT0947/ch3 3110 V Amp “1x” CORRECTED Pedestal σ = 0.019328 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.07 to 1.0 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 1010.72 +/- 90.14 p = 0.40558 +/- 0.03489 q = 1.68143 +/- 0.06435 c = 0.24595 +/- 0.003926  74342 events in signal ( 3.4% ) [We expected 2200000 −2749(cut) −2125900(pedestal fit) = 71351 events in signal. Good.]  mean signal size 0.342 Melectrons We assume the amplifier gain from SPICE: 3067 Ω. 6% low from expected result. SPICE: Expected 0.0201 Melectrons. In this run, unfortunately a small problem with negative saturation above about 1 Me. Ignore that data for fit.

Same plot except on linear scale JT0947/ch3 3110 V Amp “1x” CORRECTED

20 events, with “4x” amplifier configuration, 3110 V

JT0947/ch3 3110 V Amp “4x” Pedestal σ = 0.010583 Melectrons Charge histogram method as before. Fit pedestal first, then fit whole curve (from 0.039 to 1.15 Melectrons) to a phenomenological form (red curve) for signal ignoring electronics noise + the fixed pedestal fit. Signal in fit g(x)=b*x**p*exp(-x**q/c) b = 360.753 +/- 13.23 p = 0.24404 +/- 0.01528 q = 2.20030 +/- 0.05604 c = 0.25298 +/- 0.003507  72489 events in signal ( 3.3% ) [We expected 2200000 −1470(cut) −2127158(pedestal fit) = 71372 events in signal. Good.]  mean signal size 0.336 Melectrons We assume the amplifier gain from SPICE: 11.32 kΩ. 8% low from expected result. SPICE: Expected 0.0109 Melectrons.

Same plot except on linear scale JT0947/ch3 3110 V Amp “4x”

Conclusions part deux: Pedestal rms still corresponds very well with expected value from measured scope noise or from amplifier SPICE noise. “1x” amplifier gain looks slightly lower than SPICE predicted (6%). But, this may include a few percent for HV repeatability, resistor tolerance, AC coupling effects, nonlinearity effects, etc. I think it is close enough for our purposes. “4x” / “1x” amplifier gain matches very well to the predicted value from SPICE (3.69). I think the IRSX measurements should agree on this point. (Unless for instance the nonlinearities there are playing a role?)

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