Difference between revisions of "Cf252 runs with HPGe"

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= Cf-252 source description=
 
= Cf-252 source description=
−
ID:
+
Serial Number: FTC-CFZ-431
 +
Z=98
 +
Mass:A document indicates that on  03/19/1993 the Cf-252  mass was 4.2<math>\mu g</math>. ( <math>1\mu g</math> is expected to emit <math>2.3 \times 10^6 n/s</math>)
 +
 
  
 
Half Life= 2.652 years
 
Half Life= 2.652 years
  
−
Neutron fluence:
+
Neutron fluence:A document indicates that on 03/19/1993 the Cf-252  the neutron rate was measured(?) to be <math>10^{7} n/s</math>.  Based on the mass one would expect <math>4 \times (2.3 \times 10^6 n/s) = 9.2 \times 10^6 n/s</math>.
 +
 
 +
Neutron energy spectrum (from A.B.Smith et.al, Physics. Rev. Vol 108 #2 pg 411-414, 1957 [[File:PhysRev108p411957.pdf]]):
 +
 
 +
[[File:Cf-252_NeutronE_PhysRevV108Pg412_1957.png | 100 px]]
  
 
Decay:  Cf-252 undergoes alpha decay to Curium (cm-248) 96.9% of the time.  The rest of the time it will undergo spontaneous Fission emitting 3.7 neutrons on average per fission.
 
Decay:  Cf-252 undergoes alpha decay to Curium (cm-248) 96.9% of the time.  The rest of the time it will undergo spontaneous Fission emitting 3.7 neutrons on average per fission.
 +
 +
 +
 +
The Fission Fragment Yield as a function Fission fragment Atomic Number (<math>Z</math>) and Atomic Mass Number (<math>A</math>) from Wahl, A., At. Data and Nuc. Data Tab., vol. 39, (1988) .
 +
 +
[[File:Cf252-FissionProductsRate_NucDatTable1988.png | 200 px]]
 +
 +
most likely observable isotopes:
 +
 +
40<Z<45 and  53<Z<58
 +
 +
==Previously measured Gamma spec==
 +
 +
[[File:Cf-252GammaSpec_100keV-1MeVA.gif | 100 px]][[File:Cf-252GammaSpec_1-2MeV.gif | 100 px]][[File:Cf-252GammaSpec_2-3MeV.gif | 100 px]][[File:Cf-252GammaSpec_4-5MeV.gif | 100 px]]
 +
 +
Fragments to try and observe:
 +
 +
<math>{A \atop Z} X_N</math> =
 +
Ac-228
 +
 +
<math>{214 \atop 83} Bi_{131}</math>
 +
Bi-214
 +
 +
Tl-208
  
 
== HpGe distribution==
 
== HpGe distribution==
 +
 +
 +
Test Run 5603 may be seeing Bi-214 line 1145 keV
 +
 +
[[File:r5602-5603Overlay.png | 100 px]]
  
 
==HpGe Neutron Damage==
 
==HpGe Neutron Damage==
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 +
==HpGe Singles measurement==
 +
 +
Measure the energy distribution observed by the HpGe detector
 +
 +
Determine optimal neutron shielding between HpGe detector and Cf-252 source
 +
 +
==Small Scintillator position==
 +
 +
Determine how close the small scintillator can be positioned without having detected neutrons overwhelm detector photons.  Want to be sure the small scintillator is detecting photons most of the time
 +
 +
== Determine timing resolution of HpGe Detector==
 +
Below is a time difference plot of coincidence 511 keV photons from Na-22. The Na-22 source is 3" from both the  timing scintillator and the HPGe detector. The following photon energy cut is applied: 508 < erg < 514. All coincidence events disappear if the source is removed, so there are virtually no accidentals. (run 5736).
 +
 +
[[File:HPGe timing.png|700px]]
 +
 +
== search for fission fragment gammas ==
 +
I completed a run with the CF252 source where all events were 3-fold coinc between the HPGe detector, a small timing scintillator nearby the source, and a hit in at least one neutron detector (run 5743). Neutrons were then discriminated in software by ToF, which is made possible by means of the timing scintillator. 
 +
 +
I compared the photon energies of events with a neutron hit, to energies from a non-coincidence background subtracted CF252 spectrum (runs 5775 & 5773). I made a histogram for both cases and normalized the integrals to unity in oder to allow me to search for gammas that occur overwhelmingly when a neutron is coincident.  I failed to see any pronounced energies occurring only when in coincidence with a neutron.
 +
 +
 +
[[File:CoincVSNONCoinceCF252.png| 850px]]
 +
 +
==Estimate run time for efficiency measurement==
  
 
=Runlist=
 
=Runlist=
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|-
 
|-
 
| 5614 || 654  || 15  ||  0    ||  13885  || Co-60 source.  Coincidence between HPGe and timing PMT || Calibration
 
| 5614 || 654  || 15  ||  0    ||  13885  || Co-60 source.  Coincidence between HPGe and timing PMT || Calibration
 +
|-
 +
| colspan="7" | '''Total n flux: 13885 n/cm^2'''
 +
|}
 +
 +
 +
==01/01/17==
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CF-252 source is kept at a fixed distance while the thickness of poly between src and HPGe is increased by increments of 2".
 +
{| border="1" style="border-collapse: collapse; padding: 5px; text-align: center "
 +
!Run # !! RunTime [sec] !! distance[cm] !! n flux <math>[\frac{n}{cm^2}]</math><br><math>=\frac{n_{rate}t}{4\pi d^2}</math> <br>([[Cf-252 rates table|<small>Cf252 rates</small>]]) || Integral <br>n flux <br> <math>[\frac{n}{cm^2}]  </math> ||configuration || num events || notes 
 +
|-
 +
| 5633 || 372 || rowspan="6" |49 || 235 || 235 || No poly. || 303,929 ||
 +
|-
 +
| 5634 || 371 ||  235 || 470 || 2" poly. || 250,495 ||
 +
|-
 +
| 5635 || 371 || 235 || 705 || 4" poly. || 202,942 ||
 +
|-
 +
| 5637 || 397 ||256 || 956 || 6" poly. ||181,667 ||
 +
|-
 +
| 5638 || 371 ||  235 || 1190 || 8" poly. || 147,801 ||
 +
|-
 +
| 5639 || 371 ||  235 || 1425 || 10" poly. || 134,095 ||
 +
|-
 +
| 5641 || 110  || - || - || - || -- ||  || CO-60 + Na-22 cal. run
 +
|-
 +
| 5642 || 291  || - || - || - || -- ||  ||background run
 +
|-
 +
|}
 +
 +
==01/12/17 - 01/18/17==
 +
 +
Discriminator threshold for timing PMT, neutron PMT's, and HPGE are 50, 35, & 70 mV, respectively.  When calculating neutron flux I reduced the result by factor of 4 because of the 4" of poly shielding the HPGe detector. 
 +
 +
{| border="1" style="border-collapse: collapse; padding: 5px; text-align: center "
 +
!Run # !! RunTime [sec] !! distance[cm] !! n flux <math>[\frac{n}{cm^2}]</math><br><math>=\frac{n_{rate}t}{4\pi d^2}</math> <br>([[Cf-252 rates table|<small>Cf252 rates</small>]]) || Integral <br>n flux <br> <math>[\frac{n}{cm^2}]  </math> ||configuration  || notes 
 +
|-
 +
| 5743 || 57515 || rowspan="3" |  10 || 218000|| 218000 || CF252 src. 4" Poly. 3-fold coincidence between timing scint., HPGe, and at least one neutron PMT.  || -
 +
|-
 +
| 5766 || 1546 || 6000 || 224000|| CF252 src. 4" Poly. '''2-fold''' coincidence between timing scint and  HPGe  || -
 +
|-
 +
| 5773 || 780  || 3000 || 227000 || CF252 src.  4" Poly. '''no coincidence'''|| -
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|-
 +
| 5775 || 780 || N/A  ||rowspan="3" | 0|| rowspan="3"| 227000 || '''No src'''. 4" Poly. no coincidence|| Background run
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|-
 +
| 5769 ||21097  || rowspan="2" | 10  ||'''Na-22'''. 4" Poly. '''2-fold''' coincidence between timing scint and  HPGe|| Na-22 calibration run
 +
|-
 +
| 5770 || 1211 ||'''C0-60'''. 4" Poly.  2-fold coincidence between timing scint and  HPGe|| Co-22 calibration run
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 +
 +
 
|-
 
|-
 
|}
 
|}
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[[2nCor 44|go back]]
 
[[2nCor 44|go back]]
−
'''Total n flux: 13885 n/cm^2'''
 

Latest revision as of 06:45, 19 January 2017

Detector efficiency measurements using a Cf-252 source.

Cf-252 source description

Serial Number: FTC-CFZ-431 Z=98 Mass:A document indicates that on 03/19/1993 the Cf-252 mass was 4.2[math]\mu g[/math]. ( [math]1\mu g[/math] is expected to emit [math]2.3 \times 10^6 n/s[/math])


Half Life= 2.652 years

Neutron fluence:A document indicates that on 03/19/1993 the Cf-252 the neutron rate was measured(?) to be [math]10^{7} n/s[/math]. Based on the mass one would expect [math]4 \times (2.3 \times 10^6 n/s) = 9.2 \times 10^6 n/s[/math].

Neutron energy spectrum (from A.B.Smith et.al, Physics. Rev. Vol 108 #2 pg 411-414, 1957 File:PhysRev108p411957.pdf):

Cf-252 NeutronE PhysRevV108Pg412 1957.png

Decay: Cf-252 undergoes alpha decay to Curium (cm-248) 96.9% of the time. The rest of the time it will undergo spontaneous Fission emitting 3.7 neutrons on average per fission.


The Fission Fragment Yield as a function Fission fragment Atomic Number ([math]Z[/math]) and Atomic Mass Number ([math]A[/math]) from Wahl, A., At. Data and Nuc. Data Tab., vol. 39, (1988) .

Cf252-FissionProductsRate NucDatTable1988.png

most likely observable isotopes:

40<Z<45 and 53<Z<58

Previously measured Gamma spec

Cf-252GammaSpec 100keV-1MeVA.gifCf-252GammaSpec 1-2MeV.gifCf-252GammaSpec 2-3MeV.gifCf-252GammaSpec 4-5MeV.gif

Fragments to try and observe:

[math]{A \atop Z} X_N[/math] = Ac-228

[math]{214 \atop 83} Bi_{131}[/math] Bi-214

Tl-208

HpGe distribution

Test Run 5603 may be seeing Bi-214 line 1145 keV

R5602-5603Overlay.png

HpGe Neutron Damage

I made a page discussing neutron damage to the HPGe detector (Fast_neutron_damage_to_HPGe_Detector) as a function of the total amount of fast neutrons per [math]cm^2[/math] irradiated on the detector face. [math]5 \times 10^6 n/cm^2[/math] is a factor of 10 below the point where damage was first observed in an experiment.

RunPlan

Object: Determine if an HpGe detector can be using to tag neutrons and identify the isotope species parent of the neutron


HpGe Singles measurement

Measure the energy distribution observed by the HpGe detector

Determine optimal neutron shielding between HpGe detector and Cf-252 source

Small Scintillator position

Determine how close the small scintillator can be positioned without having detected neutrons overwhelm detector photons. Want to be sure the small scintillator is detecting photons most of the time

Determine timing resolution of HpGe Detector

Below is a time difference plot of coincidence 511 keV photons from Na-22. The Na-22 source is 3" from both the timing scintillator and the HPGe detector. The following photon energy cut is applied: 508 < erg < 514. All coincidence events disappear if the source is removed, so there are virtually no accidentals. (run 5736).

HPGe timing.png

search for fission fragment gammas

I completed a run with the CF252 source where all events were 3-fold coinc between the HPGe detector, a small timing scintillator nearby the source, and a hit in at least one neutron detector (run 5743). Neutrons were then discriminated in software by ToF, which is made possible by means of the timing scintillator.

I compared the photon energies of events with a neutron hit, to energies from a non-coincidence background subtracted CF252 spectrum (runs 5775 & 5773). I made a histogram for both cases and normalized the integrals to unity in oder to allow me to search for gammas that occur overwhelmingly when a neutron is coincident. I failed to see any pronounced energies occurring only when in coincidence with a neutron.


CoincVSNONCoinceCF252.png

Estimate run time for efficiency measurement

Runlist

12/29/16

No poly was used to shield the HPGe detector.

Run # RunTime [sec] distance[cm] n flux [math][\frac{n}{cm^2}][/math]
[math]=\frac{n_{rate}t}{4\pi d^2}[/math]
(Cf252 rates)		 Integral
n flux
[math][\frac{n}{cm^2}] [/math]		 configuration notes
5609 4060 30 6850 6850 Cf252 in. Coincidence between HPGe and timing PMT A ToF spectrum exists but is very hectic. Problem may be that the TDC stop is determined by a widened timing PMT pulse in coinc. with a HPGe pulse that has high timing jitter.
none 1250 26 2800 9655 Not taking data during this time.
5611 2509 30 4230 13885 Cf252 in. Coincidence between HPGe and timing PMT. TDC stop was changed to always be 1200 ns after PMT timing pulse, otherwise same setup as 5609. ToF looks good. Neutron rate approx. 3 Hz for detector 90.
5613 10025 15 0 13885 Na-22 source. Coincidence between HPGe and timing PMT Calibration
5614 654 15 0 13885 Co-60 source. Coincidence between HPGe and timing PMT Calibration
Total n flux: 13885 n/cm^2


01/01/17

CF-252 source is kept at a fixed distance while the thickness of poly between src and HPGe is increased by increments of 2".

Run # RunTime [sec] distance[cm] n flux [math][\frac{n}{cm^2}][/math]
[math]=\frac{n_{rate}t}{4\pi d^2}[/math]
(Cf252 rates)		 Integral
n flux
[math][\frac{n}{cm^2}] [/math]		 configuration num events notes
5633 372 49 235 235 No poly. 303,929
5634 371 235 470 2" poly. 250,495
5635 371 235 705 4" poly. 202,942
5637 397 256 956 6" poly. 181,667
5638 371 235 1190 8" poly. 147,801
5639 371 235 1425 10" poly. 134,095
5641 110 - - - -- CO-60 + Na-22 cal. run
5642 291 - - - -- background run

01/12/17 - 01/18/17

Discriminator threshold for timing PMT, neutron PMT's, and HPGE are 50, 35, & 70 mV, respectively. When calculating neutron flux I reduced the result by factor of 4 because of the 4" of poly shielding the HPGe detector.

Run # RunTime [sec] distance[cm] n flux [math][\frac{n}{cm^2}][/math]
[math]=\frac{n_{rate}t}{4\pi d^2}[/math]
(Cf252 rates)		 Integral
n flux
[math][\frac{n}{cm^2}] [/math]		 configuration notes
5743 57515 10 218000 218000 CF252 src. 4" Poly. 3-fold coincidence between timing scint., HPGe, and at least one neutron PMT. -
5766 1546 6000 224000 CF252 src. 4" Poly. 2-fold coincidence between timing scint and HPGe -
5773 780 3000 227000 CF252 src. 4" Poly. no coincidence -
5775 780 N/A 0 227000 No src. 4" Poly. no coincidence Background run
5769 21097 10 Na-22. 4" Poly. 2-fold coincidence between timing scint and HPGe Na-22 calibration run
5770 1211 C0-60. 4" Poly. 2-fold coincidence between timing scint and HPGe Co-22 calibration run



go back

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