Integration of a Clover Detector with the
necessary electronics and computer program
to utilize the ADDBACK method
An SP496 and Capstone Research Project
Midshipman First Class Jack Hathaway
Advised by
Assistant Professor Daryl Hartley, Ph.D.
Co60
Emitted Beta Particle
Unstable Co60
Beta Decay
1173 γ-ray
Emitted Gamma rays
Unstable Ni60
Energy
1332 γ-ray
Stable Ni60
Time
So how do we ‘see’ all of this happening?
What kind of detector do we need?
When my advisor was a student…
Bell bottoms were cool…
The Beetles first appeared on stage…
…and nuclear physicists used Sodium Iodide (NaI) Detectors…
High Density = Great Efficiency
Poor Energy Resolution from
detection system
While I was busy watching Transformers…
Nuclear physicists developed Germanium (Ge) Crystal Detectors…
Low Density = Low Efficiency
Great Energy Resolution from
detection system
Can we have the
Low Density = Low Efficiency
best of both?
Great Energy Resolution from
detection system
High efficiency
and
good resolution?
Clover detector
An array of four Germanium Crystals, physically and electronically independent
25 cm
Clover
Detector
Source Location
Anode
Cathode
Channel Number
The Basic Electronics:
Spec Amp
ADC
Crystal 1
Number
Of
Counts
Crystal 1
0
Crystal 2
600
Crystal 3
0
Crystal 4
0
KMAX
Program
Crystal 2
Number
Of
Counts
The KMAX program displayed 5 counts,
but there were only 3 Events….
Channel Number
Channel Number
Were
there
5 gamma rays orCrystal
only
Crystal
3
4 3?
Number
Of
Counts
Number
Of
Counts
Channel Number
Channel Number
Mission:
Utilize the Clover Detector as an array rather
than four single detectors to give the
researcher the best data possible
Solution:
Integrate the Clover Detector into the
necessary electronics and create a
computer program to utilize the
ADDBACK Method
What is ADDBACK?
Addback Flash created by Dave Campbell, Florida State University
Coding ADDBACK
Computer Input
Channel Number
Crystal 1
0
Crystal 2
600
Crystal 3
0
Crystal 4
0
Step 1:
Define an event
Event 1
Each event corresponds to a single gamma
ray interacting with the detector.
One Gamma ray = One Event = One Coincidence Window
Step 2: Creating an electronic Coincidence Window
Output group 1
Spec Amp
Fast Amp
Output group 2
Logic ‘OR’
Gate
Gate
Delay
Generator
Output to Computer
Event 1
Channel Number
Crystal 1
600
Crystal 2
0
Crystal 3
400
Crystal 4
200
1 2 34
ADC Gate
Inputs
Analog to Digital Converter
Step 3: Applying calibrations
Crystal 1
Counts
Channel
Number
Energy
Event 1
Channel Number
Crystal 1
600
Crystal 2
0
Crystal 3
400
Crystal 4
200
Crystal 2
Counts
Channel
Number
Energy
Crystal 3
Counts
Channel
Number
Energy
Crystal 4
Counts
Channel
Number
Energy
Step 4: Executing ADDBACK
Event 4
1
2
3
Channel Number
Energy
Crystal 1
600
1350
0
560
1332
0
Crystal 2
0
800
0
746
Crystal 3
400
1150
0
412
1173
0
Crystal 4
200
0
210
201
0
251
ADDBACK = 1332
560
0 + ++
0746
0+
0 ++
1173
+412
00+++0+251
0=201
=1332
=1173
=997
1173
Totals
ADDBACK
Separate Crystals
Event 1
1173
Event 1
560, 412, 201
Event 2
1332
Event 2
1332
Event 3
1173
Event 3
1173
Event 4
997
Event 4
746, 251
Peak to
Background
3:1 ratio (actual 25%)
2:5 ratio (actual 14%)
Results
Results
Future Goals
- Longer Runs
- Proton Resonance
- Polarization
Acknowledgements
Advisor: Assistant Professor Daryl Hartley, Ph.D.
Witty quips and technical advice: Professor Jeff Vanhoy, Ph.D.
Stunts and Modeling: MIDN 1/C Drew Barker, roommate
Scratch-work slide
125
250
400
650
Background
Detector pictures?
Clover Picture
The Basics:
Coding ADDBACK
Event 3
1
2
Spec Amp
ADC
Crystal 1
Number
Of
Counts
KMAX
Program
Crystal 2
Number
Of
Counts
The KMAX
1 Count program displayed 5 counts,
1 Counts
2
Count
but there were only 3 Events….
Channel Number
Channel Number
Were
there
5 gamma rays orCrystal
only
Crystal
3
4 3?
Number
Of
Counts
1 Count
Channel Number
Number
Of
Counts
1 Count
Channel Number
Double outputs, same signal from each crystal
Pre-Amp
Interior to the Clover
Detector
What is a Coincidence Window?
32 microseconds
Ekg thingermabober of science!
Gate
Delay
Generator
ADC
Gate
Input
Output
Question slide on the PMT NaI detectors