Introduction

With the renewed interest in the Monte Carlo pulse parameterization, and beginning the process of constant determination I have written a set of routines which parameterize the buckeye pulse shape for cross-talk, convolution with ion drift(1/t+2.1), and further convolution with a square wave representing drift electron arrival. The routines are available at: Buckeye buckeye_utils.tar.gz. A description of the routines can be found in: README.

Delta Function Amplifier Response

The buckeye amplifier/shaper is a 5-pole semi-Gaussian shaper with one extra pole and one extra zero added for tail cancellation.

For a pure 5-pole semi-Gaussian shaper the pulse is given by the expression t**4*exp(-t/p0), and the peaking time is given as 4/p0. This is of course modified slightly by adding the tail cancellation zero/pole.

During production of the Buckeye ASICs p0,p1, and z1 were fit for each chip (~200,000). Central values and error(sigma) were found to be:

	Central Value	Chip-2-Chip	Channel-2-Channel
p0	0.03654	+/-0.00027	+/-0.00016
Gain	1.000	+/-0.021	+/-0.0092
Time Delay	0.0	+/-1.13
p1	0.0054
z1	0.00347

The tail cancellation pole p1 and zero z1 are very correlated, and it makes no sense to quote error values.

Delta Function Cross Talk

To parameterize cross talk calibration data taken at the pre-Slice test setup at Point 5 was fit using Minuit. Adding an extra pole and an extra zero seems to fit the data reasonably (well within 1%).

Physically this corresponds to the pulsed strip coupled through a parallel resistor capacitor to the cross talk strip, with the cross talk strip resistively coupled to ground. I was unable to find another pole/zero combination which fit as well. The fits were performed by initially fitting the pulse strip shape using a gain, time offset, p0,p1, and z1. These values were then fixed and the cross talk strips were fit using Nct,tr, and tct. The resulting fits can be found in pulses.ps Overall fit parameters can be found below.

p0	0.347	+/-0.0005
p1	0.00546	+/-0.0013
z1	0.0035	+/-0.0001
Nct	0.330	+/-0.007
tct	0.0463	+/-0.0020
tr	0.00326	+/-0.00054