Digital Hadron CalorimeterCosmic Ray Test Stand

As of 9am05/12/2003Note: 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

• 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

• 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

3

62

4

87

5

14%

10%

11%

11%

11%

15%

5%

10%

5%

13%8%

6%8%

7%

Standard Configuration with no black paper

Cells 5,8,6 covered by black paper layers separated by paper

Effect of covering cells with black paper to reduce optical crosstalk between cells

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 4Expect 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