Multiplexing with the 1720 Digitizer

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# Multiplexing with the 1720 Digitizer - PowerPoint PPT Presentation

Multiplexing with the 1720 Digitizer. Setup. 0. Digitizer. fifo. I). 1. amp. 2. We send the same signal into 3 channels of the digitizer to make sure each sees the same thing and we see the same pulses from all 3 channels. 0. Digitizer. fifo. II). amp. fifo. 1. 2. fifo.

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Presentation Transcript

### Multiplexing with the 1720 Digitizer

Setup

0

Digitizer

fifo

I)

1

amp

2

We send the same signal into 3 channels of the digitizer to make sure each sees the same thing and we see the same pulses from all 3 channels

0

Digitizer

fifo

II)

amp

fifo

1

2

fifo

multiplexed data

Some of the data are multiplexed. The bigger picture is that each digitizer channel can handle 2 or 3 PMTs if we multiplex

them and electronics become cheaper, but it also should perform as well with the multiplexed data as it does with the non-multiplexed.

Single PMT into 3 Different Digitzer Channels

Ratios of measured integral in each channel to the measured integral in channel 0 on an event by event basis.

Channel 0

Channel 1

Channel 2

Up to 1 % change depending on which channel is

selected from the digitizer.

Energy spectrum from

constant time integral

Single PMT- Undelayed, Delayed, Delayed and Multiplexed

time T

time T

Ratio 1/0

Ratio 2a/0

Ratio 2b/0

Ratio 2b/1

integral_0

Channel 0

Delay D

integral_1

Channel 1

Channel 2

integral_2a

integral_2b

Same energy spectrum as previous

page constant time integral

Various ratios of const time width integrals.

Ratio of delayed intgrals and ratio of undelayedintegrals

are ~ .5% FWHM. While comparing undelayed

to delayed are much worse, ~4% FWHM with large tails.

The delay is ~200 ns nd the integral window is ~120ns.

Signal Defects

After Pulsing

All of these examples

fall into the delayed

signal integral window,

which is very common thing. Though all of these are from the single PMT into 3 digitizer channels, hence the three graphs of the same picture.

After Pulsing

+ Ringing

Ringing

+ Noise

Lower Threshold

137Cs Compton Edge

Background 40K Compton Edge

Noise (radio station), PMT ringing, and

PMT after pulses shows up more for the lower size signals, hence the worse resolution of the various ratios.

High threshold energy spectrum from

constant time integral