Neutron Production in THICK Targets Induced by High Energy Ions: Unexpected Effects and Perspectives

Reinhard Brandt

Kernchemie, Fachbereich Chemie, Philipps Universität, D-35037 Marburgand

Fundraising-Initiative Kernchemie, Marburg(www.fundraising-initiative.de)

1.) Neutron experiments at the Synchrophasotron, JINR, Dubna, Russia

2.) Neutron experiment at the Bevalac, LBL, Berkeley, California

3.) Suggested neutron experiments, in order to design safe neutron shieldings and target systems

for high intensity machines.

[prepared for EU-Parlament in Brussels: „Nuclear Energy Workshop“, Nov.12.2008]Brussels.ppp.11.08

THE COLLABORATION PRODUCING THIS WORK:

R. Brandt, V.A. Ditlov, K.K. Dwivedi, W. Ensinger,E. Ganssauge, Guo Shi-Lun, M. Haiduc, S.R. Hashemi-Nezhad, H.A. Khan, M.I. Krivopustov, R. Odoj, E.A. Pozharova, V.A. Smirnitzky, A.N. Sosnin, W. Westmeier, M. Zamani(Marburg - ITEP/Moscow – Washington –Beijing –Bucharest – Sydney -

Dubna - Islamabad – Jülich – Thessaloniki)

Interactions of relativistic heavy ions in THICK heavy element targets and some unresolved problems.

Physics of Elementary Particles and Atomic Nuclei, 39(2), (2008), 507[Original version, published by JINR, Dubna (Ru)] and

Physics of Particles and Nuclei, 39(2), (2008), 259 – 285, and

Studies with SSNTD and nuclear chemistry on nuclear reactionsinduced by relativistic heavy ions in THICK targets: a review

“Proc. 23rd International SSNTD Conf., Beijing, 2006”, in Radiation Measurements. 43, (2008), 132 - 138

Neutron counting results

Tableau 1: Neutron emission from THICK Pb-targets. The total number of thermal neutrons n, generated by one

primary ion( 1-H, 2-H, 4-He, or 12-C ) in a very thick lead target (Φ = 20 cm and L = 60 cm), moderated within 1 m3 paraffin

and measured by Vassilkov et al. in Dubna (1983)

3.7 : 1 (5.0 0.3): Such a result cannot be calculated. This constitutes an “unresolved problem”.

Ion Mass A Thermal neutrons nat ET/A=1 GeV

Thermal neutrons nat ET/A=3.7 GeV

n at (ET/A=3.7 GeV)

n at (ET/A=1.0 GeV)

H 1 16.5 0.5 49.4 1.9 3.0 0.2

H 2 45.8 1.2 157 3 3.4 0.2

4 71.2 2.8 277 9 3.9 0.2

C 12 129 5 641 22 5.0 0.3

Tableau 2: Experimental setup, called GAMMA-2.Introduced in 1995 , since 2007 an IAEA Benchmark target. This target allowed in Dubna two-parameter measurements:

1.) Nuclear destruction within Cu via radiochemistry2.) neutron measurements with chemical & SSNTD sensors

La-sensors

U-sensors

Chemical sensors

Various SSNTD-sensors

Tableau 3 : Calculated total neutron numbers N for GAMMA-2 according to the DCM/CEM model.

Comparison with experimental results for 44 GeV 12-C:

The experiment in Dubna gave N=(700±140) neutrons, the model calculated 280 neutrons for the Pb-target.

12-C

Tableau 4: Neutron fluences at the Bevalac accerator LBL (Lawrence Berkeley Laboratory, USA) around a 20 cm THICK Cu target

Irradiated with 72 GeV 40-Ar in the year 1987.Facts are: Secondary fragments destroy Cu nuclei stronger when they are produced by 72 GeV 40-Ar as compared to 44 GeV 12-C. This “unresolved

problem” has been observed clearly with radiochemical methods. The neutron fluence during the above irradiation (72 GeV) was unexpectedly VERY LARGE, but the measured neutron fluence was never published.

What has been “cooking” in Berkeley?

Protocol from memory: LBL irradiation with5*E8 ions/sec of 72 GeV 40Ar + THICK Cu at 10.3.87. from 816 -- 900 a.m. (44 min)B – Bevalac acceleratorH –HILAC (Heavy Ion Accelerator)1 -- 184“ Synchrocyclotron (not working)2 – Cafeteria3 – Bldg 70: Nuclear Chemistry4 – Bldg 50: Nuclear Physics5 – Administration6 – Exit downhill to the UC campus

B

H

100 m

1

2

3

4

56

Tableau 5: What happened close to the Bevalac in detail during the irradiation on March 10. 1987 with 72 GeV 40-Ar (5*108 ions/sec) ?

816 a.m.: start irradiation

830: neutron alarm on TOP of Bevalac (Monitor turned off)

840: neutron alarm in the

HILAC (Monitor turned off)

900.00 : Ar-beam turned off

The experimental hall & 104 to Fe Bevalac

are well shielded with massive concrete in

4π geometry

72 GeV Ar-ion beam

Target: 20 cm Cu block, 8 cm Ф

Certain result:

The accelerator concrete shielding was sufficient for decades of experiments with THIN targets.

This shielding was utterly insufficient for THICK target experiments

Cu

Tableau 6 : Summary,

At present one can calculate the ratio for experimental to theoretical neutron fluence only with the following accuracy

in the ion energy range of

------ about 1 to 10 GeV (ADS: “Energy-plus-Transmutation”( E&T) [Krivopustov], JINR, Dubna, etc) only up to +(22 ± 14) %,

Hashemi-Nezhad, NIMA, 501 (2008), 517

------ about 10 to 100 GeV not-at-all, due to the “excess neutrons” observed in Dubna. In addition, one MAY have seen enhanced

“complete nuclear destruction” into individual nucleons during the interaction of >200 GeV 238U in THICK targets (next foil).

This would increase the neutron production further.

Tableau 7 : The complete destruction of

220 GeV 238-U:“Interactions of

relativistic 238-U and light targets”. H.A. Khan, et al.

NIM (1991) B61, 497.-----------

The FAT and roundetch pits are due to

U ions and FF:NOT of interest!

THE TINY ETCH PITS are of

INTEREST:“Complete Nuclear

DESTRUCTION ?? or“Particle therapy ??”

Tableau 8: Outlook

We need to know experimental results about the neutron emission

from THICK targets ( examples: Cu, Pb, natU ) irradiated with

ions having E(total) > 10 GeV.

WHY ?

• To have proper radiation protection shielding for high energy and high intensity ion accelerators under construction

• To find out, how much “excess neutrons” (compared to

standard model calculations) one observes experimentally

for ions with energies E(total) > 10 GeV

New technological applications are conceiveable.

• To find out, WHY we observe “excess neutrons”