Testing and Calibration of Testing and Calibration of Silicon Strip DetectorsSilicon Strip Detectors

Stephanie N. SimpsonResearch Experiencesfor Undergraduates

Michigan State University

August 6, 2003

The High Resolution ArrayThe High Resolution Array

20 telescope array20 telescope array

One thin, single sided silicon strip One thin, single sided silicon strip detector, one thick, double sideddetector, one thick, double sided

4 Thallium4 Thallium--doped doped CsI CsI ((TlTl) detectors) detectors

A Look at A Look at HiRAHiRA

http://groups.nscl.msu.edu/hira/hira/HiRA-homepage.htm

Why Why HiRAHiRA??

The The HiHigh gh RResolution esolution AArray is versatile:rray is versatile:

Detects alphas, deuterons, protons, Detects alphas, deuterons, protons, isotopes through neon (Z=10)isotopes through neon (Z=10)

Transfer reactions, resonance Transfer reactions, resonance spectroscopy,spectroscopy, multimulti--fragmentation,fragmentation, etcetc..

Various configuration capabilitiesVarious configuration capabilities

A Look at A Look at HiRAHiRA

http://groups.nscl.msu.edu/hira/hira/HiRA-homepage.htm

Silicon strip detectorsSilicon strip detectors

Semiconductor detectorsSemiconductor detectors

Excitation of electrons produces signalExcitation of electrons produces signal

Electrons “migrate” towards the anode Electrons “migrate” towards the anode while holes move towards the cathode while holes move towards the cathode via and electric fieldvia and electric field

Signal detected by the electronics of the Signal detected by the electronics of the detectordetector

The two problems:The two problems:Sometimes the deposit of a particle in Sometimes the deposit of a particle in

the silicon results in energy being the silicon results in energy being detected on two neighboring stripsdetected on two neighboring strips

Why does this occur?Why does this occur?

Occasionally it has been seen that the Occasionally it has been seen that the signal of a particle on one strip signal of a particle on one strip corresponds to a signal of opposite corresponds to a signal of opposite polarity found on a neighboring strippolarity found on a neighboring strip

Why does this occur?Why does this occur?

The ExperimentThe Experiment

Thin sided silicon detectorThin sided silicon detector

5.4 5.4 meV meV Am 241 alpha sourceAm 241 alpha source

Each set of channels sent through Each set of channels sent through individual preamplifiers, shapers, and individual preamplifiers, shapers, and discriminators and digitized to be read as discriminators and digitized to be read as spectra.spectra.

Splitter BoardsSplitter Boards

Shapers have inputs of 16 channels with Shapers have inputs of 16 channels with a ground for eacha ground for each

Silicon has 34 channels: 32 signals and Silicon has 34 channels: 32 signals and two ground two ground

Splitter boards divide 34 channel signal Splitter boards divide 34 channel signal into two groups of 16 with a ground for into two groups of 16 with a ground for eacheach

Convenient layout for testing “the two Convenient layout for testing “the two problems”problems”

The The Splitter Splitter BoardsBoards

OddEven

The Presence of Charge The Presence of Charge SplittingSplitting

Two nonTwo non--inverting shapers for both sets inverting shapers for both sets of 16 channels of 16 channels

Spectrum created that plots neighboring Spectrum created that plots neighboring strips versus each otherstrips versus each other

Look to see if energy from one signal Look to see if energy from one signal was deposited on two strips…….was deposited on two strips…….

The Presence of Charge The Presence of Charge SplittingSplitting

Energy (arbitrary units)

Energy (arb itra ry un its)

A comparison of band counts/strip A comparison of band counts/strip counts versus gap width/strip width counts versus gap width/strip width shows there is a correlation between the shows there is a correlation between the twotwo

Comparison of Band/Strip Ratio to Gap/Strip Ratio

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Channels 1-2 through 31-32

Ratio

Val

ue Band/Strip 160Ratio of Gap Width to Strip WidthAvg Band/Strip 160

Channels 1-32

Opposite Polarity SignalsOpposite Polarity Signals

A second spectrum was taken using one A second spectrum was taken using one nonnon--inverting shaper and one inverting inverting shaper and one inverting shapershaper

The inverting shaper inverted any The inverting shaper inverted any opposite polarity signals occurring on opposite polarity signals occurring on that set of 16 channelsthat set of 16 channels

Look to see if any signals are present Look to see if any signals are present from that set of channels…….from that set of channels…….

Opposite Polarity SignalsOpposite Polarity Signals

Energy (arbitrary units)

Energy (arbitrary units)

340 1/3 45 1/2

???

Ratios of opposite polarity counts/total Ratios of opposite polarity counts/total and gap width/silicon width did not and gap width/silicon width did not correlate wellcorrelate well

Negative Counts/Total and Gap Width/Silicon Width

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Channel

Ratio Negative Counts to Total Counts (y/total)

Gap width to total width

ConclusionsConclusionsA correlation was found between the A correlation was found between the

signals appearing on neighboring strips signals appearing on neighboring strips and the gap to strip ratioand the gap to strip ratio

Opposite polarity signals were found to Opposite polarity signals were found to appear on the thin silicon detectorappear on the thin silicon detector

No relationship was found between the No relationship was found between the presence of opposite polarity signals and presence of opposite polarity signals and the gap to strip ratiothe gap to strip ratio

More study is needed!!More study is needed!!

AcknowledgementsAcknowledgements

DrDr. Bill Lynch, . Bill Lynch, DrDr. Mike . Mike FamianoFamiano, and , and Mark Wallace for their expertise and Mark Wallace for their expertise and guidance during this projectguidance during this project

The National Science FoundationThe National Science Foundation

DrDr. Stump and Michigan State University. Stump and Michigan State University