Difference between revisions of "Cf252 runs with HPGe"

From New IAC Wiki
Jump to navigation Jump to search
Line 108: Line 108:
 
| 5639 || 371 ||  235 || 1425 || 10" poly. || 134,095 ||
 
| 5639 || 371 ||  235 || 1425 || 10" poly. || 134,095 ||
 
|-
 
|-
| 5640 || 371 || - || - || - || 10" poly. ||  || Back ground run
+
| 5641 || || - || - || - || -- ||  || CO-60 + Na-22 cal. run
 
|-
 
|-
 
|}
 
|}

Revision as of 22:17, 10 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

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 - - - -- CO-60 + Na-22 cal. run



go back