Digital Hadron Calorimeter
Cosmic Ray Test Stand
As of 9am05/12/2003
Note: axes on scatter plots are reversed
Status
• Multichannel system is working
• Good data on 13 channels but 3 channels very low gain
• 1 other channel has fiber damaged - only cladding damaged
Analysis Software
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Wrote my own software using Visual Basic to display data
Can display by data by cell or by PMT channel
Can switch between top layer and bottom layer of cells
Show small histogram bin=5
Show large histogram bin=1
Primitive method of finding pedestal, pedestal cutoff, first peak cutoff
Scatter plots of all data, data above pedestal cutoff, data above first
peak cutoff
Ch4 vs
No
pedestal
No pedestal
and no first
curve
No pedestal
and no first
curve
First Peak: Single Photoelectron or Crosstalk?
Summary of Initial Results
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It is a primitive tracking calorimeter
Most show two peaks one of them is close to pedestal
Is first peak single photoelectron, crosstalk, or noise?
Not noise because I took samples with all all photocathodes of PMT
covered by black paper and only get narrow pedestal
• Crosstalk can be
– optical crosstalk in cells
– optical or electrical crosstalk in PMT
Four tests to determine cause of first peak
• Cover 8 channels with black paper
• Stimulate PMT channel with multiple fibers driven by LED to
determine cross talk at PMT
• Cover 3 cells with black paper and put black paper between layers to
reduce optical crosstalk between cells
• Stimulate cells with source
To test crosstalk at PMT
• Covered 2 columns of PMT photocathodes with black paper between
photocathode and fiber
• Collect Cosmic Rays overnight
Crosstalk at PMT
Standard configuration
Photocathodes 5-8 and 13-16 covered
Channel 4 stimulated by several fibers driven by LED
Suggests crosstalk at PMT
Effect of covering cells with black paper to reduce
optical crosstalk between cells
8
7
3
4
6
5
2
Standard Configuration
with no black paper
Cells 5,8,6 covered by black paper
layers separated by paper
14%
11%
15%
10%
8%
10%
11%
8%
5%
11%
13%
6%
5%
7%
Stimulating Cells with Sr90 Source
• Source over cell 4 (center)
• If due to radiation or optical crosstalk we’d expect 6 and 8 to be the
same since both are covered by black paper and cells are same distance
from cell 4
• The response at channel 8 is higher because it is closer to channel 4 at
the PMT
Scatter plots with Sr90 source over cell 4
Expect 6 and 8 to be the same since both are
covered by black paper and cells are same distance
from cell 4
Ch.8 is closer to 6 at PMT so
effect is probably due to crosstalk at PMT
Summary
• Previous test indicate that first peak is partly due to optical crosstalk at
cells and crosstalk at PMT
• Need to determine if PMT crosstalk is optical or electrical
• Need to quantify theses effects
• May be other effects to study
Next Steps
• Make quantitative measurements of different forms of crosstalk
• Enhance software
• Analyze data collected with absorber