The 2-Body Photodisintegration Reaction 4He(,n)3He below 30 MeV

John Kelley, R. Raut, G. Rusev,

S.C. Stave, A.P. Tonchev,  W. Tornow

Triangle Universities Nuclear Laboratory

North Carolina State University

Duke University

“Equality” vs Inequality of 4He(,n/p)3He/3H

What are the Implications?

• Charge Symmetry

• Isospin Mixing

Present State

Compton backscatter FEL photons from electrons in a storage ring FEL.

4He(,3He)n below 30 MeV at the High Intensity -ray Source (HIGS)

Photon Flux from Plastic Scintillator PaddleEfficiency measured by comparison with NaI

10” x 12” NaI detectorWell understood efficiency

Pb

Pb10 mmCollimator

-ray beam

Plasticscintillatorpaddle / PMT

Experimental SetupPMT

3He-Xe gas scintillator

Pb

Pb

PlasticScintillator paddle/PMT10 mm

Collimator

-ray beam

Active 4He/Xe 5 cm diameter scintillation cell

E

(MeV)

Pressure

PSI.

Xe/He E3He

(MeV)

3He range

mm

27 (710 4He/40 Xe) 0.056 1.6 0.8

27.5 750 0.056 1.73 0.9

28 750 0.056 1.85 1.0

50 mm diameter

max

4He/Xe scintillation cell vs

Xe scintillation cell “target out”

Photon-induced reaction thresholds (in MeV)Isotope Nat. Abundance (%) (,p) ( (,n) (,2n) (n)xenon isotopes 128 1.92 8.17 1.77 9.61 16.84 11.19 131 21.18 8.82 2.55 6.61 15.87 8.85 136 8.87 9.93 3.66 7.99 14.44 11.73magnesium isotopes 24 78.99 11.69 9.31 16.53 26 11.01 14.15 10.61 11.09oxygen isotopes 16 99.762 12.13 7.16 15.67 18 0.200 15.94 6.23 8.05 He isotopes 4 99.762 19.81 - 20.58

“charged” kinetic energy

Edge effects ignored

Lt 1 MeV

1-3 MeV (1.6)

5-10 MeV

10-20 MeV

E=27 MeV4He+ -> 3He(1.6 MeV)& n (4.8 MeV)

Atomic effects

High Rate/ High ThresholdAnti-Pileup Circuit

FIFO C

FD

AMP

FIFO

PULSER

AMP

FIFO

AMP

GDG

3He Cell

Linear

Gate

Busy

Inhibit

AMP

inhibit

High Threshold – minimize multi-pulse pileup in the CFDLinear Gate

t~100 ns – (with inhibit t~10 us) minimize pileup in Spectroscopic Amplifier

Scaler

Scaler

Computer

Busy

Paddle

Logic

Scaler

Results

• Proof of principle• Beamtime expected in the next quarter