PAA CoincidenceCounting

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ADC non-linearity

Canberra Model 9615 < 0.04% (integral) over 2usec

Canberra Model 9633 < 0.025% (integral) < 0.9% (differential), +10V range into 1kOhm, 8192 channels, 100 usec signal width => 100 pC/chan

CAEN V792 < 0.1% (integral), 200 fC/chan

CAEN digitizer VX1492, 14 bit, 10 Volt range


Coinc Scope pictures

First pict with ADC gate

Two HpGe detectors were used to detect coincidence gammas from Co-60 on 6/14/2013.

Co-60 will beta decay to Ni-60 giving off two gammas in coincidence having energies of 1173 and 1332.5 keV. The scope pictures below record the pulses from the HpGe detector that are in coincidence. I would have expected the charge output by the HpGe detector to be similar for the two gammas, but there are some that have less than half the charge. The could be the beta particles from the decay reaching one of the detectors in coincidence with one of the gammas.


A061413 CPAA coin.pngB061413 CPAA coin.pngC061413 CPAA coin.png


First Singles Spectrum

Detector B

R5399-5400 overlay.pngR5399-5400 Caloverlay.png

Detector 180-3

R5377-5378 overlay.png


50 keV Energy resolution from an HpGe detector??

I think the inverting amp is too noisy:

Noise 62613.png


The Signal is about 400 mV and the above noise is 37 mV peak-to-peak and it is syncronized with my integrate gate

Noise A62613.png

The voltage variations of the timing amp output in the region of the integrate gate are about +/- 10 mV


Noise B62613.png

Singles Spectrum (2nd attempt)

Using detector 180-3

HV = -2800 Volts

Run 5446, Co-60 and Na-22 sources are in at the same time, attenuation is 18 db, 1 Mev photon peaks are around 3000 -> 3500 channels in ADC spectrum

Two Co-60 Lines

Mean 2.94555e+03 +/- 7.23197e-01 Sigma 7.61455e+01 +/- 8.86697e-01

Mean 3.63275e+03 +/- 8.39279e-01 Sigma 7.45542e+01 +/- 1.04796e+00

1.2 meV na-22 line

Mean 3.37891e+03 +/- 1.07859e+00 Sigma 6.26450e+01 +/- 1.73063e+00

Run 5447, Na-22 source, attenuation is 18 db, 1 Mev photon peaks are around 3000 -> 3500 channels in ADC spectrum Mean 3.38431e+03 +/- 1.29456e-01 Sigma 1.12914e-01 +/- 2.59220e-02

Run 5448, Na-22 source, attenuation is 14 db, 0.511 Mev photon peaks are around 1000 channels in ADC spectrum

Run 5449, Na-22 source, attenuation is 12 db, 0.511 Mev photon peaks are around 2500 channels in ADC spectrum

Mean 2.60181e+03 +/- 8.10190e-01 Sigma 5.97964e+01 +/- 6.63405e-01


Run 5450, Co-60 source, attenuation is 12 db, 1 Mev photon peaks are around 3000-> overflow channels in ADC spectrum


Run 5451, Co-60 source, attenuation is 13 db, 1 Mev photon peaks are around 2500 -> 3500 channels in ADC spectrum

Low energy 1.2 MeV peak

Mean 2.64173e+03 +/- 1.35816e+00 Sigma 1.03518e+02 +/- 1.49690e+00

High energy 1.3 MeV peak Mean 3.33157e+03 +/- 1.36696e+00 Sigma 1.01444e+02 +/- 1.15611e+00


Run 5452, Na-22 source, attenuation is 13 db, 1 Mev photon peaks are around 2500 -> 3500 channels in ADC spectrum

Mean 3.02266e+03 +/- 1.53757e+00 Sigma 5.26142e+01 +/- 1.61646e+00


Run 5453, NO source, attenuation is 13 db, 1 Mev photon peaks are around 2500 -> 3500 channels in ADC spectrum, run started at 17:18:27 on July 23 ended on July 24 at 15:34:05


Run 5484, Na-22 and Co-60 source, attenuation is 14 db, 1 Mev photon peaks are around 2600 -> 3600 channels in ADC spectrum, Na-22 and Co-60 peaks are separable unlike in detector B

Run 5484, Na-22 source, attenuation is 8 db, 0.5 Mev photon peaks are around 2000 channels in ADC spectrum

Using detector B

HV = +4520 Volts

Run 5466, Na-22 source, attenuation is 17 db, 1 Mev photon peaks are around 2300 channels in ADC spectrum


Run 5470, Co-60 source, attenuation is 17 db, 1 Mev photon peaks are around 2300 channels in ADC spectrum


Run 5471 & 5472, Na-22 and Co-60 sources both in, attenuation is 17 db, 1 Mev photon peaks are around 2300 channels in ADC spectrum


Run 5474, Na-22 source, attenuation is 12 db, 0.5 Mev photon peaks are around 1000 channels in ADC spectrum


The above runs used the same input lines that were used for detector 180-3, Now I put Detector B through its own signal lines and the attenuation needed changes

Run 5477, Na-22 source, attenuation is 9 db, 1 Mev photon peaks are around 3000 channels in ADC spectrum


Run 5478, Co-60 source, attenuation is 9 db, 1 Mev photon peaks are around 3000 channels in ADC spectrum

Run 5480, Na-22 source, attenuation is 3 db, 0.5 Mev photon peaks are around 1500 channels in ADC spectrum

Singles SPectrum 3rd attempt (Peak sensing ADC)

Using the CAEN 785 peak sensing ADC I was able to increase the dynamic range and take positive going pulses.

Below are the first two spectra with sources and almost no discrimination


Detector 180-3

Run Number Description
5632 Na-22 1 uCi source
5633 Co-60 1 uCi Source R5632-5633 spect.png
5634 Co-60 1 uCi Source, set threshold on Ortec Const Fraction Timing Disc model 2035A to 20 mV
5635 Co-60 1 uCi Source, set threshold on Ortec Const Fraction Timing Disc model 2035A to 10 mV
5636 Na-22 1 uCi Source, set threshold on Ortec Const Fraction Timing Disc model 2035A to 10 mV R5635-5636 spect.png


Calibration Fit

Spectrum of 60Co, peaks at 1.17 and 1.33 MeV

Co60: http://ie.lbl.gov/toi/nuclide.asp?iZA=270060

Two peaks at 1173.2374 keV and 1332.5015 keV

Na22 Spectrum: 1274.532 keV

Na22: http://ie.lbl.gov/toi/nuclide.asp?iZA=110022

Na22 emits: 0.510998928(11) MeV

Run Number Source Energy (keV) Fit
5636 Na-22 510.998928 1215 R5636 511.png
5635 Co-60 1173.2374 2709 R5635 1173.png
5636 Na-22 1274.532 2937 R5636 1275.png
5635 Co-60 1332.5015 3068 R5635 1333.png


Fit:

slope = 2.26 +/- 0.003
intercept= 62.45 +/- 2.59
Looks like I have 3 keV resolution or less on detector 180-3
Run Number Source Energy (keV) Fit
5636 Na-22 510.998928 1215 R5636Cal 511.png
5635 Co-60 1173.2374 2709 R5635Cal 1173.png
5636 Na-22 1274.532 2937 R5636Cal 1275.png
5635 Co-60 1332.5015 3068 R5635Cal 1333.png

Coincidence Tests

Detector B is in ADC Ch9, TDC18


Detector 180-2 is in ADC CH5, TDC16


Run Number Description
5644 Na-22 1 uCi Source, set threshold on Ortec Const Fraction Timing Disc model 2035A to 10 mV
5645 Co-60 1 uCi Source, set threshold on Ortec Const Fraction Timing Disc model 2035A to 10 mV
5667 First Coincidence run, a coincidence is required in the logic unit, the coincidence window is about 1usec wide (probably a lot of accidentals), source is Co-60 1 uCi, CPAA App 080913.png, I have increased the CFD lower threshold to remove, via hardware, photon energies below 800 keV(Detector 180-3 CFD lower threshold was 200 and detector B was 150, the rate was about 6 Hz, run time was 14 minutes 22 seconds
5668 Now the logic unit is switched to OR mode, everything else is the same as run 5667, the rate was about 1 kHz, run time was 14 minutes 25 seconds
5669 Now the logic unit is switched to OR mode, and the CFD lower threshold is reduce to about 100 keV (10 on the CFD lower threshold pot) , everything else is the same as run 5667, the rate was about 3 kHz, run time was 10 minutes, The ROC crashed probably due to the 3 kHz rate.
5670 Now the logic unit is switched to AND mode, and the CFD lower threshold is reduce to about 100 keV (10 on the CFD lower threshold pot) , everything else is the same as run 5667, the rate was about 100 Hz, run time was 13 minutes 56 seconds
5671 same as run 5670 but now there is a 100 uCi Co-60 source, the rate was about 10 Hz, run time was 1 minutes, I think there is a lot of pile up so ignore this run
5672 same as run 5670 but now there is NO source, the rate was about 2 Hz, run time was 1 minutes, I think there is a lot of pile up so ignore this run

Proposed Apparatus

We propose to acquire two 14 bit digitizers (flash ADCs), a muli-hit time-to-digital converter, and the associated NIM electronics needed to supplement our current VME based data acquisition system. The availability of precision analog digitizers and pipeline time to digital converters allows the construction of a data acquisition system to record the pulse shape and time information that will allow the reconstruction of individual coincidence events. The most common method used to record photon spectroscopy information does so by accumulating events thereby loosing any temporal information. We propose a coincidence counting system which records the wave form of each coincidence event along with a time stamp. The system will allow a post data taking analysis that can increase the coincidence time constraint beyond the original requirement and ascertain the degree of confidence in identifying the decay under consideration.

Isotopes for CPAA

Au

neutron knockout

Knock a neutron out of natural gold such that an excited state of Au-196 remains that will undergo electron capture to Pt-196 with a half life of 6 days or 2% of the time it can be left in a meta stable state with two possible half lifes of 8 seconds or 9 hours.

[math]{197 \atop\; }Au (\gamma,n){196 \atop \; }Au[/math]

Au-196 Meta state

The 8 sec metastable state of Au-196 decays through the emission of only one 84.66 keV photon.

The 9.6 hour metastable state has high intensity gamma lines at 147.81 keV and 188.27 keV.

Pt-196 decay EC decay

[math]{196 \atop \; }Au \rightarrow {196 \atop \; }Pt^* [/math] with a half life of 6 days.

The Pt-196 has a 355.73 dominant (100% relative intensity) gamma line that goes to the 256.2 state giving off a 97.3 keV photon


proton knockout

[math]{197 \atop\; }Au-79 (\gamma,p){196 \atop \; }Pt-78[/math]

Filling Ln2

Date Detector
8/7/13 B I filled Detector B for 20 minutes with the valve open 1/2 turn and the detector completely warm.
8/8/13 B Detector B was still cold after 26 hours, I filled it at 1/2 turn flow rate for 15 minutes


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