Gamma Spectroscopy

4/26/12

H. Herrmann (LANL)

- 2 -

e-

Next Steps• Cherenkov detectors

Energy thresholdedGas limited to >2.5 MeVSolid limited to <~0.2 MeVAerogel might span the gap

• Real g-ray spectroscopy (Energy resolved)

X-ray framing camera + CCDX-ray framing camera + CCDSourceSource

θBragg=12oθBragg=12o

Sagittally Bent HOPG crystal

M. Moran, RSI 56, 1066 (1985)

Compton Spect. (>2 MeV) Pixelated Single-Hit “Furlong” (>0.1 MeV?)

Bent Crystal(<1.5 MeV)

Energy resolution would provide valuable information to the Ignition Campaign

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 5 10 15 20

Gam

mas

/Neu

tron

/(0.

1 M

eV b

in)

Gamma-Ray Energy (MeV)

DT

Fu

sio

nD

(n,

)

12C

(n,

)

12 C

(n,n

’)

12C

(n,

)

Hohlraum/TMP n-

Calculated DT Gamma-Ray Spectrum

•Spectral uncertainties call for energy resolution- GRH is only energy thresholding, not resolving

•Be Ablator R from impurity 16O(n,n’) at 6.1, 6.9, 7.1 MeV

• Spectral lines may provide:- 16.75 MeV fusion DT yield- 4.44 MeV 12C(n,n’) CH Ablator R- 15.58 MeV D(n,) Fuel R

DT Fusion -ray spectrum needs to be mapped out better

D + T 5He*

5He*16.75 MeV

4.5 MeV

0 MeV

-0.96 MeV 4He + n5He

1

0

1/0 2.3 ± 0.4

0 5 10 15 200

0.2

0.4

0.6

0.8

1

Gamma-Ray Energy (MeV)

Inte

ns

ity

(a

. u

.)

1

0

G-total/Gn = (4.2 ± 2.0) × 10-5

10-5

10-4

101 102 103 104

Buss '63Kosiara '70Bezotosnyi '70Cecil '84 ( only)Morgan '86 ( only)Kammeraad '93Balbes '94Parker '2011Present Work

D-T

Bra

nch

ing

Rat

io

Deuteron Beam Energy (keV)

Center of Mass Energy (MeV)6 60 6 102 6 103

presentwork

0

0

Y. Kim (LANL), C. Horsfield (AWE)

• GCD mapping of spectrum at OMEGA used assumed line shapes determined by R-Matrix analysis (G. Hale, LANL

• Needs to be verified by spectroscopy

0.0E+00

5.0E-06

1.0E-05

1.5E-05

2.0E-05

2.5E-05

3.0E-05

10 15 20

Gam

mas

/Sou

rce_

neut

ron/

MeV

Gamma-Ray Energy (MeV)

DT

D

C

Hohl/TMP

Total

0.5 MeV binning

Slide 5

0.5 MeV resolution (E/E 3%) at high energy is adequate

Slide 6

0.0E+00

5.0E-06

1.0E-05

1.5E-05

2.0E-05

2.5E-05

3.0E-05

10 15 20

Gam

mas

/Sou

rce_

neut

ron/

MeV

Gamma-Ray Energy (MeV)

DT

D

C

Hohl/TMP

Total

0.5 MeV binning

0.5 MeV resolution (E/E 3%) at high energy is adequate

1.0E-04

1.0E-02

2.0E-02

3.0E-02

4.0E-02

5.0E-02

0 5 10

Gam

mas

/Sou

rce_

neut

ron/

MeV

Gamma-Ray Energy (MeV)

DT

D

C

Hohl/TMP

Total

0.5 MeV binning

Slide 7

0.5 MeV resolution at low energy (adequate, but GCS will do better at 3%)

Operated by Los Alamos National Security, LLC for NNSA

U N C L A S S I F I E D

Mix-dependant -ray lines could aid Ignition Campaign

reaction E (g MeV) Application13C(d,n)14N* 4.91, 5.69 13C layers in CH or doped in Be

9Be(d,n)10B* 2.8, 3.4 , 4.49, 6.03 Be Capsule

9Be(a,n)12C* 4.4 Be Capsule

• MeV alpha-particles born in the DT burn and MeV knockon deuterons and tritons interacting with ablator material (C or Be)

• Reactions emitting gammas sensitive to stopping power with sg>~10 mb/sr/gamma-ray:

A. Hayes, LANL

• 2-Temp LPI x-rays spectrum (Kruer model)– 3 orders-of-mag more x-ray energy below 300

keV than above– Nearly 4 orders-of-mag more energy in LPI x-

rays than Prompt Nuclear -rays– Comparable energy in x-rays & -rays above

~300 keV• Empirically, there’s ~3x more FFLEX signal

from -rays than x-rays at >250 keV• GRH background is dominated by <250 keV

x-rays

Challenge: measure high energy -ray in background of other -rays & LPI x-rays

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02

keV

/keV

/sr

Ex (MeV)

LPI x-rays(Kruer)

Prompt -raysYDTn = 5e14(DT, D,C,Al,Si,Au)

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02

E (

J) a

bove E

x

Ex (MeV)

LPI x-rays

Prompt -rays-rays of interest:

12C(n,n’)

DT- D(n,)

Slide 10

Physics-based Requirements:

Topic Requirement

Resolution E/E 5%

Sensitivity Req’d n Yield

100 e- in bins of interest:Y > 3e14 for 12C- (at R12C 200 mg/cm2)

Y > 3e15 for DT-0

Y > 1e16 for DT-1 and D(n,g)

Binning 12 energy bins

Temporal Response <1ns

SNR >5

Energy Range Total: 2-25 MeVSingle Shot: 2/3Ehigh to Ehigh (e.g., 12-18 MeV)

04/19/2023 11

Option: FURLONG, does not need high neutron yield…

Each detector records less than one gamma ray, many detectors.

Build a spectrum by summing over many detectors.

Painful, but very high quality data.

LaBr3 “Brilliance” detectors. The Best…. But VERY expensive. Need to build factory, share with GSI / FAIR plans

Very good energy resolution Detector array planned at FAIRW. Stoeffl (LLNL)