2 pictures first (9/10/2009)

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First data from ADC125 module8/24/2009

Input

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Output

Note: Range is 0-16384 (14 bits), two LSB are zero here (a 12 bit assembly)

Peaking here is designed/desired (cable response equalization). Keep in mind there is no cable installed in this measurement.

Output noise level (open input)

σ=2.20 (as 12-bit: σ=0.55)

Input pulse through capacitor to GAS-1(top is detail)See GlueX-doc-931-v2 for details (same setup used here)

Combined response of GAS-1/GPC-01, cable, and ADC125 to 94 electron x 5x104 signal with t0=1.38 ns

Connector assembly problem corrected; first data from preamp & ADC125 together9/10/2009

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eDon’t worry about the tail:• ADC125 component values to be adjusted, when

• final preamp• final cable length

• also we can cancel the tail digitally in the FPGA

Combined response of GAS-1/GPC-01, cable, and ADC125Single 4096-point acquisition noise spectrum (no averaging)

• The overall structure is as expected from the preceeding pulse plot… 3 points on the leading edge implies that the bandwidth is ≈1/3 Nyquist.• But here you can see that there really is insignificant noise above the cutoff frequency ≈25 MHz

• So all the waveform information is present in the digital data – the algorithms have a chance• My opinion is that this is a bit too conservative: want to raise the bandwidth by 20-30% here, will improve timing resolution w/o any noticeable compromise to charge resolution

• Or we can drop the sample rate and hence the raw data volume• Also: hard to draw conclusions yet w/o averaging, but no anomalous peaks are seen here – no EMI issues (on lab bench)