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12-00121

Testing for the Photon Doppler Broadening Data SamplingBug in MCNP5/X

Brian C. KiedrowskiForrest B. BrownMorgan C. WhiteD. Kent Parsons

MCNP Documentation

Testing for the Photon Doppler Broadening Data Sampling Bug in MCNP5/X

Brian C. Kiedrowski, Forrest B. Brown,Morgan C. White, D. Kent Parsons

1 Introduction

MCNP5/X has the capability to perform photon Doppler broadening to incorporate the effect of boundelectrons on photon scattering. This effect is generally important if energy spectra or detector responses aredesired for photons in the tens to hundreds of keV energy range. In the Fall of 2011, a diligent MCNP usernoticed that the sampling routines in MCNP were inconsistent with the data for sampling which atomicshell the electron is bound. The data are provided in probability density function (PDF) format, whereasMCNP sampled the data as if they are in a cumulative density function (CDF) format, leading to erroneousresults.

Future versions of MCNP (i.e., MCNP6) will internally convert the PDF data into CDF data and thesampling will be performed consistently. However, to support existing users so that they do not have toupdate and revalidate a new version of MCNP, new data files have been provided with the atomic shells inCDF representation, which will allow versions prior to MCNP6 to account for photon Doppler broadeningcorrectly. The details of the new data libraries are discussed in Los Alamos memo LA-UR-12-00018, “FurtherNotes on MCPLIB03/04 and New MCPLIB63/84 Compton Broadening Data For All Versions of MCNP5”.For the purposes of this report, the old data have the extensions of .03p and .04p, whereas the new temporarydata have the corresponding extensions .63p and .84p.

Before releasing the new data files, testing has been performed to both assess the quality of the new dataand the impact of the fix to inform users if they need to upgrade their data libraries. Hundreds of CPU hoursof testing was performed by the MCNP development team in addition to that done by the LANL data team,and the general conclusion is that the effect on the spectra is generally small, but noticeable. Furthermore,as a general trend, the previous, incorrect method in MCNP was doing too little Doppler broadening. Thenew data will generally produce results with even smoother edges than previously predicted.

Note that this does not necessarily mean the answers are more predictive of reality, it merely means thatMCNP is correctly sampling the data as provided. It may be in some cases the new data might produce worseanswers because the atomic shell probability sampling is done strictly on the number of electrons occupyingeach atomic shell and does not account for any screening effects. In either case, users that care about detailedphoton detector spectra in the tens to hundreds of keV energy range are encouraged to update.

2 Description of the Tests

Six types of tests are performed to assess the quality of the data. The test problems are run with only .04pand .84p sets unless otherwise noted. The tests are as follows:

1) The first set of tests assesses what values the incorrect sampling of the data is returning within MCNP.The PDF and CDF data is randomly sampled as MCNP does numerous times and the frequency of samplingeach shell is obtained.

2) Short 100k history runs of all elements from Z = 1-100 to ensure that MCNP runs to completion andno serious errors are encountered. Both the .63p and .84p libraries are run.

3) For 30 selected elements (to span much of the periodic table, capture trends, and focus on commondetector materials), a 90 keV photon source is placed in a 1 cm radius ball of matter at a density of 1.0 g/cc.These are run in MCNP for 1 billion histories each. The energy spectrum of the photon flux in the ball (F4tally) and the photon energy deposition in the ball (F8 tally) are tallied. The thick-target bremsstrahlungapproximation is used. The elements used are H, He, Li, Be, B, C, N, O, F, Na, Si, P, S, K, Ga, Ge, As, Br,Cd, In, Te, I, Cs, La, Ce, Nd, Lu, Hg, Pb, and U.

4) For 10 selected elements, a 195 keV photon beam is directed at a thin (nearly infinite in the z-directionwith a thickness of 0.01 cm and density 1.0 g/cc) slab target using 100 million histories. The energy spectrum

1

of the backscattered photon current (F1 tally) is tallied. This simulation uses explicit electron transportmodeling. The elements used are H, C, Na, Si, Fe, Ge, I, La, W, and U.

5) The photon energy flux spectrum and energy deposition for a 88 keV photon source on a SiLi detectorusing 1 billion histories. Explicit electron transport is performed.

6) The photon energy flux spectrum and energy deposition for a 80 keV photon source on a Ge detectorusing 100 million histories. Explicit electron transport is performed.

3 Results of the Tests

The results of the six test case types are given. The version of the software is MCNP5-1.60 with a threaded(OMP) and non-MPI compilation that is a direct copy of the DVD image distributed by RSICC. All the prob-lems are run on a Linux AMD x84, 64-bit processor using four threads. The results are usually labeled “NoDoppler .84p”, “Doppler .04p”, or “Doppler .84p”. This means the new data with no Doppler broadening,the old data with the PDF representation, and the new temporary data with the CDF representation.

For brevity, this section gives plots of only a few of the results. Interested readers should consult AppendixA for a complete listing of figures.

1) The tests involving which shell is sampled by the bad sampling (of the PDF data, assuming the dataare in CDF format) versus what is sampled with appropriate data shows a consistent trend of stronglyoversampling the outermost shell. The oversampling tends to worsen as the atomic number Z increases.Tests show that the sampling on the new (CDF) data returns approximately (within statistical noise) of theactual sampling probabilities given by the PDF. Results iodine are shown in Fig. 1.a. The true probabilities(and what is sampled with CDF data) is given by the blue boxes and the bad sampling with the PDF data isgiven by the red lines. For iodine, many of the shells are not sampled at all currently, and about 90 percentof the time, the outermost shell is sampled, as opposed to the true sampling frequency of about 6 percent.Fig. 1.b shows the probability of sampling the outermost shell the correct and wrong methods. The generaltrend is that as Z increases, the discrepancy between what MCNP should have been sampling and what itdid sample grows.

2) The tests of short 100k history runs of the new data from elements Z = 1-100 show that all run tocompletion with no errors. This is important for quality assurance purposes.

3) The results of the tests show a general trend that as Z increases, sampling the PDF as it was a CDFdid not result in enough Doppler broadening. As a test on the data and sampling, hydrogen and heliumare particularly interesting because there should be no impact from the fix since there is only one shell tosample. Indeed, both the old and the new data produce exactly the same result.

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Shell Index

Shell Probability Density (Iodine)

Correct SamplingWrong Sampling

(a)

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Outermost Shell Sampling


(b)

Figure 1: (a) Sampling of shells for iodine. (b) Outermost shell sampling probabilities.

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Photon Energy (MeV)

90 keV Photons in Sodium Ball

No Doppler .84pDoppler .04pDoppler .84p

(a)

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Energy Deposition (MeV)



(b)

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Photon Energy (MeV)

90 keV Photons in Germanium Ball


(c)

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1e-07

1e-06

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(d)

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0.1

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Photon Energy (MeV)

90 keV Photons in Mercury Ball


(e)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

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(f)

Figure 2: Cell flux and energy deposition tallies in balls of a few elements.

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Photon Energy (MeV)

195 keV Photon Backscatter Off Carbon Target


(a)

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Photon Energy (MeV)

195 keV Photon Backscatter Off Iron Target


(b)

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Photon Energy (MeV)

195 keV Photon Backscatter Off Lanthanum Target


(c)

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Photon Energy (MeV)

195 keV Photon Backscatter Off Tungsten Target


(d)

Figure 3: Photon backscatter off thin targets of a few elements.

1e-11

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Photon Energy (MeV)

SiLi Detector (88 keV Source)


(a)

1e-10

1e-09

1e-08

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(b)

Figure 4: (a) Photon cell flux and (b) energy deposition inside SiLi detector.

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1e-14

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Photon Energy (MeV)

Germanium Detector (80 keV Source)


(a)

1e-09

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(b)

Figure 5: (a) Photon cell flux and (b) energy deposition inside Ge detector.

Results of photon flux and energy deposition for sodium, germanium, and mercury are displayed in Fig.2. For the flux tally, there is an increase in the amount of broadening observed in the Compton edges withincreasing Z. For the energy deposition (analogous to a detector signal), it appears that germanium exhibitsthe most impact, and results of elements with similar Z such as gallium and arsenic show similar behavior.This is probably because of the intensity of the photopeak and other features versus the edges. For detectorresponse type problems, materials such as gallium-arsenide and germanium are likely candidates for beingprone to having different results.

4) The photon backscatter problems show a similar trend, that the gap between the amount of Dopplerbroadening MCNP should have been predicting to what it does with the CDF data increases with increasingZ. Results for carbon, iron, lanthanum, and tungsten are given in Fig. 3.

5) The photon flux and the photon plus electron energy deposition tallies for the SiLi detector are given inFig. 4. It appears the differences are quite small around the edges, with a difference of less than ten percent.For most applications, this is probably a negligible difference. This confirms much of the observations seenin test groups 3 and 4; the differences there for the lighter elements are small for them as well.

6) The photon flux and the photon plus electron energy deposition tallies for the Ge detector are given inFig. 5. The difference around the edge of the photon flux is about as large as 30 percent, which is typicallyquite small for this application. The difference around the lower energy edge of the energy deposition isabout as large as 150 percent, which may by a large enough difference for a user to be concerned about.

4 Conclusion and Recommendation to Users

Versions prior to MCNP6 have a bug in the photon Doppler broadening routines that assumes CDF data,when they are in fact PDF data. Modified data sets with a .63p and .84p extensions have been releasedto provide a backward compatible fix to the issue. Several test problems have shown that the effect is thatMCNP would overly select the outermost shell, and the issue becomes more extreme as Z increases. Theeffect on calculational results is that MCNP was doing less Doppler broadening than it should have beendoing, and the effect tends to grow with increasing Z as well, but that depends on the problem.

Generally speaking, anyone concerned with photon detector spectra where the photons are in the energyranges of tens to hundreds of keV should upgrade to the latest mcplib. Those interested only in neutronphysics problems, or higher energy photons for shielding and dose applications are probably not impactedby this defect.

Acknowledgments

Thanks to Avneet Sood and Clell J. (C.J.) Solomon for providing some of the MCNP input files and insightsinto detector calculations.

5

Appendix A: Complete Listing of Result Plots

In addition to the plots not provided in the main text, larger versions of the figures in the text are included inthis appendix. Fig. 6 contains larger versions of the PDF versus CDF sampling problems, the ball problemsspan Figs. 7 to 36, the photon backscatter problems span Figs. 37 to 46, Fig. 47 is a larger version of theSiLi detector plots, and Fig. 48 is a larger version of the Ge detector plots.

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Shell Probability Density (Iodine)


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Outermost Shell Sampling


(b)

Figure 6: (a) Sampling of shells for iodine. (b) Outermost shell sampling probabilities.

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Photon Energy (MeV)

90 keV Photons in Hydrogen Ball


(a)

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90 keV Photons in Hydrogen Ball


(b)

Figure 7: Cell flux (a) and energy deposition (b) tallies in a Hydrogen ball.

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Photon Energy (MeV)

90 keV Photons in Helium Ball


(a)

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90 keV Photons in Helium Ball


(b)

Figure 8: Cell flux (a) and energy deposition (b) tallies in a Helium ball.

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Photon Energy (MeV)

90 keV Photons in Lithium Ball


(a)

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90 keV Photons in Lithium Ball


(b)

Figure 9: Cell flux (a) and energy deposition (b) tallies in a Lithium ball.

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Photon Energy (MeV)

90 keV Photons in Beryllium Ball


(a)

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90 keV Photons in Beryllium Ball


(b)

Figure 10: Cell flux (a) and energy deposition (b) tallies in a Beryllium ball.

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Photon Energy (MeV)

90 keV Photons in Boron Ball


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90 keV Photons in Boron Ball


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Figure 11: Cell flux (a) and energy deposition (b) tallies in a Boron ball.

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90 keV Photons in Carbon Ball


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Figure 12: Cell flux (a) and energy deposition (b) tallies in a Carbon ball.

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90 keV Photons in Nitrogen Ball


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Figure 13: Cell flux (a) and energy deposition (b) tallies in a Nitrogen ball.

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90 keV Photons in Oxygen Ball


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90 keV Photons in Oxygen Ball


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Figure 14: Cell flux (a) and energy deposition (b) tallies in a Oxygen ball.

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90 keV Photons in Fluorine Ball


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90 keV Photons in Fluorine Ball


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Figure 15: Cell flux (a) and energy deposition (b) tallies in a Fluorine ball.

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Figure 16: Cell flux (a) and energy deposition (b) tallies in a Sodium ball.

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90 keV Photons in Silicon Ball


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90 keV Photons in Silicon Ball


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Figure 17: Cell flux (a) and energy deposition (b) tallies in a Silicon ball.

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90 keV Photons in Phosphorous Ball


(a)

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90 keV Photons in Phosphorous Ball


(b)

Figure 18: Cell flux (a) and energy deposition (b) tallies in a Phosphorous ball.

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Photon Energy (MeV)

90 keV Photons in Sulfur Ball


(a)

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90 keV Photons in Sulfur Ball


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Figure 19: Cell flux (a) and energy deposition (b) tallies in a Sulfur ball.

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l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Potassium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Potassium Ball


(b)

Figure 20: Cell flux (a) and energy deposition (b) tallies in a Potassium ball.

21

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Gallium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Gallium Ball


(b)

Figure 21: Cell flux (a) and energy deposition (b) tallies in a Gallium ball.

22

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)



(a)

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly




(b)

Figure 22: Cell flux (a) and energy deposition (b) tallies in a Germanium ball.

23

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Arsenic Ball


(a)

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Arsenic Ball


(b)

Figure 23: Cell flux (a) and energy deposition (b) tallies in a Arsenic ball.

24

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Bromine Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Bromine Ball


(b)

Figure 24: Cell flux (a) and energy deposition (b) tallies in a Bromine ball.

25

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Cadmium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Cadmium Ball


(b)

Figure 25: Cell flux (a) and energy deposition (b) tallies in a Cadmium ball.

26

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Indium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Indium Ball


(b)

Figure 26: Cell flux (a) and energy deposition (b) tallies in a Indium ball.

27

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Tellurium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Tellurium Ball


(b)

Figure 27: Cell flux (a) and energy deposition (b) tallies in a Tellurium ball.

28

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Iodine Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Iodine Ball


(b)

Figure 28: Cell flux (a) and energy deposition (b) tallies in a Iodine ball.

29

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Cesium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Cesium Ball


(b)

Figure 29: Cell flux (a) and energy deposition (b) tallies in a Cesium ball.

30

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Lanthanum Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Lanthanum Ball


(b)

Figure 30: Cell flux (a) and energy deposition (b) tallies in a Lanthanum ball.

31

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Cerium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Cerium Ball


(b)

Figure 31: Cell flux (a) and energy deposition (b) tallies in a Cerium ball.

32

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Neodymium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Neodymium Ball


(b)

Figure 32: Cell flux (a) and energy deposition (b) tallies in a Neodymium ball.

33

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Lutetium Ball


(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Lutetium Ball


(b)

Figure 33: Cell flux (a) and energy deposition (b) tallies in a Lutetium ball.

34

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)



(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly




(b)

Figure 34: Cell flux (a) and energy deposition (b) tallies in a Mercury ball.

35

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Lead Ball


(a)

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Lead Ball


(b)

Figure 35: Cell flux (a) and energy deposition (b) tallies in a Lead ball.

36

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)

90 keV Photons in Uranium Ball


(a)

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly


90 keV Photons in Uranium Ball


(b)

Figure 36: Cell flux (a) and energy deposition (b) tallies in a Uranium ball.

37

0

1e-05

2e-05

3e-05

4e-05

5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Hydrogen Target


Figure 37: Photon backscattering off Hydrogen target.

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Carbon Target


Figure 38: Photon backscattering off Carbon target.

38

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Sodium Target


Figure 39: Photon backscattering off Sodium target.

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Silicon Target


Figure 40: Photon backscattering off Silicon target.

39

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Iron Target


Figure 41: Photon backscattering off Iron target.

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Germanium Target


Figure 42: Photon backscattering off Germanium target.

40

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Iodine Target


Figure 43: Photon backscattering off Iodine target.

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Lanthanum Target


Figure 44: Photon backscattering off Lanthanum target.

41

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Tungsten Target


Figure 45: Photon backscattering off Tungsten target.

0

5e-06

1e-05

1.5e-05

2e-05

2.5e-05

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Surfa

ce C

urre

nt T

ally

Photon Energy (MeV)

195 keV Photon Backscatter Off Uranium Target


Figure 46: Photon backscattering off Uranium target.

42

1e-11

1e-10

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)



(a)

1e-10

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly




(b)

Figure 47: (a) Photon cell flux and (b) energy deposition inside SiLi detector.

43

1e-16

1e-14

1e-12

1e-10

1e-08

1e-06

0.0001

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cel

l Flu

x Ta

lly

Photon Energy (MeV)



(a)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Puls

e H

eigh

t Tal

ly




(b)

Figure 48: (a) Photon cell flux and (b) energy deposition inside Ge detector.

44

jetform:836 - los alamos national laboratory

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