Slide 1James Christian
Instrument Research & Development
E.B. Johnson, C.M. Whitney, X.J. Chen, S.M. Vogel, E.V.D. van Loef, R. Hawrami, J.Glodo, L.S. Pandian, K.S. Shah, T.H. Prettyman, E. Benton
SBIR
– Anti-coincidence (distinguished ions from n, γ) • Scintillation material capabilities
Radiation
3
Dose • Absorbed dose (TID) • Human-equivalent dose: Tissue and Q (quality factor)
– Q: “legislated” relative biological effectiveness (RBE) for cancer endpoint: depends on E and LET
• Displacement Damage Dose (NIEL – non-ion. E loss)
• Identify Particle Type • Linear Energy Transfer (LET = ) or E • (Dose rate)
Deq = RBE × DR → Specific
Particle Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
BLAKELY, E.A., et al., Adv. Radiat. Biol. 11 (1984) 195–389.
ICRP 60 (1991a)
Interactions with HnCm Scintillator
• DPA is a “new” H18C26 material (~tissue density) • Light ∝ Absorbed Dose TID: Birks legacy (S & kB quenching) • Recoil proton (in plastic) related to neutron energy
p+ n γ
p+ (in plastic)
dx dx
Proportionality with gammas: S-term
• S-term related to gamma ray energy resolution • ~15 k photons per MeV (bright – as high as 20)
0 200 400 600 0.0
0.5
1.0
6
Characterize kB-term (protons) dE dx
• kB larger in DPA than EJ200 (C-term fixed) – More δ-ray/ionization quenching – Deviation not analysis (Experimental factors)
0 5 10 15 20 0
5
10
15
20
L
/ x/
187 MeV
50 100 150 200 0 1 2 3 4 5 6 7
kB 0.026 0.011 cm/MeV C 6.4E-6 7.9E-6 (cm/MeV)2
L/ S
(M eV
DPA EJ200
10-3
10-2
10-1
100
0 10 20 30 40 50 60 70 80
0.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
increasing LET
• Photon yield ~20 photons/keV • CLYC proportional (good gamma E-resolution)
6Li: 6Li + 1n → 3H + 4α 4.78 MeV 940 Barns 35Cl: 35Cl + 1n → 35S 0.62 MeV <1 Barn
10 100 1000
ld
energy, keV 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0
1
2
0.5
1.0
137Cs Spectra
in te
ns ity
, a rb
. u ni
CLYC emission time characteristics
• Distinguish gammas from thermal neutrons (3-He) • No p+ recoil, detect fast neutrons with 35-Cl
0 200 400 600 0.0
0.2
0.4
0.6
0.8
1.0
1.2
gamma
neutron
200
300
400
500
CLYC:Ce
gammas
neutrons
10k
20k
30k
40k
Measuring neutron energy with CLYC
200 400 600 800 1000 0 100 200 300 400 500 600
Channel
893 keV 1202 keV 1508 keV 1913 keV
0 500 1000 1500 2000 0 200 400 600
Energy (keV)
• 35-Cl (n,p) reaction • Fast Neutron Spectroscopy
13
Summary
• Interesting Scintillation Materials – Thermal and fast neutron – Distinguish p+, n, & γ – Beam results optimistic
• Compact Neutron Dosimeters and Spectrometers – Anti-coincident shield – Pulse-shape discrimination (electronics) – SSPM detectors: compact, high gain
14
15
Achievements Tested CLLBC Dosimeters at PNNL:
• Category 1 – isotopes passed, x-ray failed • Category 2 – isotopes passed, x-ray “close”
Designed Category-1 x-ray detector Received and tested new dosimeter chip Designed new compact version Developing HDD, SDD, assembly,
testing, and QC protocols: ISO 9001 compliance
Facilities: Constructed x-ray room, crystal preparation station, dry glove box, environmental chamber automation.
Met with Stan Mavrogianis and Eric Daxon at HPS meeting
-0.2 0.0 0.2 0.0
• Neutron dose important, lots of background
10-3 10-2 10-1 1 10 102 103 104 10-6 10-5 10-4 10-3 10-2 10-1
1 10
• Galactic Cosmic Rays (GCR), Solar Protons and Secondary Emission (gamma-rays, neutrons, and others)
p+ (GCR) p+
Summary