1 Proposal to the ISOLDE and Neutron Time-of-Flight Committee 33 S(n,α) 30 Si cross section...

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Proposal to the ISOLDE and Neutron Time-of-Flight Committee

33S(n,α)30Si cross section measurement at n_TOF EAR2: data below 10 keV.

Javier Praena1,2, Ignacio Porras3, Marta Sabate-Gilarte1,4,

José M. Quesada1, Hanna Koivunoro5,6 F. Arias de Saavedra3 and M. Pedrosa3

for the n_TOF collaboration

1) Universidad de Sevilla, Spain

2) Centro Nacional de Aceleradores, Sevilla, Spain

3) Universidad de Granada, Spain

4) CERN, Switzerland

5) Department of Physics, University of Helsinki, Finland

6) Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland

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1. General motivations for 33S(n,).

2. Status of the 33S(n,) cross-section data including our

previous measurement at n_TOF EAR-1.

3. Motivations for 33S(n,) at EAR-2.

4. Count rate and beam time request.

Javier Praena, INTC Nov 2014, 33S(n,) at n_TOF EAR-2

Plan of the talk.

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• Astrophysics:

• Data for alpha-nucleus potential used in HFSM

calculation of the p-isotopes nucleosynthesis. (>A).

• Origin and abundance of 36S is an open question.

• Medical physics:• 33S as cooperative target for BNCT.

Motivations for 33S(n,α)30Si measurement


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• 36S is formed by s-process or spallation processes. • The time integrated s-process flow in the region 28Si-42Ca. The process is mostly

determined by (n,) on the abundant seed nuclei, 28Si and 32S. Concerning the production of 36S is sensitive to the interplay of the branchings 33S, 36Cl and 39Ar.

• Reifarth et al [Astro. J. 528:573-581 (2000)] obtained the MACS of 34S(n,) by the activation technique showing that 34S could act as bottle-neck in this path. 34S seed is highly sensitivity to the 33S(n,).

• The origin of 36S remains an open question.

Motivations: 36S nucleosynthesis33S(n,) MACS, kT=30 keV

Auchampaugh et alPRC 12 1126 (1975)

(690170) mb TOF

Wagemans et alNPA 469 497 (1987)

(22720) mb TOF

Schatz et alPRC 51 379 (1995)

(1759) mbActivation

Woosley et alAt. D. Nucl. D. Tab. 22 371

(1978)

224 mbModel


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• Past: thermal neutron beams from nuclear reactor.• Future: epithermal neutron beams (keV) from accelerator-based neutron source.

The energy of the neutron beam is very adequate for 33S.• Experimental treatments. Finland. http://clinicaltrials.gov/show/NCT00114790

Motivations: 33S as cooperative target in NCT

10-30 keV


http://clinicaltrials.gov/show/NCT00114790

• 33S(n,α) (Q=3.1 MeV). Data are discrepant in the RRR (13-100 keV). Motivation for measuring at EAR1. • The presence 33S enhances the dose in the first centimeters in tissue. For predicting its effect at greater

depths it is mandatory data at low neutron energies.

• There is no experimental data from thermal to 10 keV. EAR2!!!!• S-33 concentration of the order of mg/g based on the addition of cystine to the culture medium, as PW Gout et al., ,

Increased cystine uptake capability associated with malignant progression of Nb2 lymphoma cells, Leukemia 11, 1329–1337 (1997). Selectivily Coderre et al., J. Nucl. Med. 27, 1157 (1986).

Motivations: 33S as cooperative target in NCT*

10-30 keV

* I. Porras Phys. Med. Biol. 53 (2008), J. Praena et al, ARI, 88 (2014) 203.

Depth (cm)

33S

Eα=3 MeV

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• Auchampaugh et al PRC 12 1126–33 1975: (n,) and (n,) from 10 to 700 keV. TOF.• Wagemans et al NPA 469 497–506 , 1987: (n,) from 10 keV to 1 MeV. TOF.• Coddens et al NPA 469 480–96 , 1987: (n,tot) from 10 keV to 2 MeV. TOF.

Auchampaugh et al Wagemans et al

Coddens et al

NO DATABELOW 10 keV

Status of 33S(n,α)30Si experimental data.


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Status 33S(n,α) data at n_TOF EAR 1 (Dec 2012)

NO DATABELOW 10 keV


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Preliminary result of our analysis. Comparison between sample 1 and

Wagemans data for the first resonance (13 keV)

The final result depends on the characterization of the mass of the samples.


Status 33S(n,α) data at n_TOF EAR 1: results

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33S(n,α)30Si experimental data at thermal

1/v extrapolation from thermal to 10 keV may provide wrong cross-section data


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Only EAF-2010 shows a resonance structure in the keV region but XS 20 times lower than experimental data. Orders of magnitude difference between the available evaluations below 10 keV

33S(n,α)30Si evaluations


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Why 33S(n,α) EAR-2?

4 cm moderator (water/borated water)

Neutrons (meV to GeV)

Pb

1 cm cooling (water)

200 m

20 m

tof

tof

EAR-1

EAR-

2

Prot

ons

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33S(n,α)30Si count rate at EAR-2 for 2e18

• The International Commission on Radiation Units and Measurements (ICRU) recommends that the radiation dose delivered should be within 5% of the prescribed dose. ICRU 1978 Dose Specification for Reporting External Beam Therapy with Photons and Electrons ICRU Report 29 (Bethesda, MD: ICRU).

• This means that uncertainty at each step within the treatment process, including cross-section data should be significantly smaller than 5%.

The counting rate has been estimated by using the experimentally measured neutron flux at EAR-2.


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• The objective is to measure the 33S(n,) cross section relative to 10B(n,) at EAR-2 to provide data below 10 keV for the first time.

• We already performed an experiment (Dec 2012) at EAR-1 to resolve the resonances (CERN-INTC-2012-006/INTC-P-322) . We have resolved the resonances and the data will be provided soon. We have no data below 10 keV.

• We have ready the samples and the detectors.

• Data below 10 keV are very important for our study of S-33 as NCT target. Simulations. Also may provide better MACS for astrophysics.

• We have estimated 2e18 protons in order to have less that 5% uncertainty in the most significant neutron energy region. (ICRU-78)

Summary of 33S(n,α) proposal at n_TOF-EAR2


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THANK YOU FOR YOUR ATTENTION

Javier Praena1,2, Ignacio Porras3, Marta Sabate-Gilarte1,4,

José M. Quesada1, Hanna Koivunoro5,6 F. Arias de Saavedra3 and M. Pedrosa3

On behalf of the n_TOF collaboration

1) Universidad de Sevilla, Spain

2) Centro Nacional de Aceleradores, Sevilla, Spain

3) Universidad de Granada, Spain

4) CERN, Switzerland

5) Department of Physics, University of Helsinki, Finland

6) Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland

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MC Simulation of absorbed and equivalent dose in water, Porras [3].

• Neutron point-like source with energy 13.5 keV (first resonance)

• Homogeneous medium (water) except a shell with 33S.

• Interactions: elastic scattering by 1H, 16O, 33S and 33S(n,).

• 1H, 16O data from EXFOR.

• 33S(n,) from conservative value [5]; ([5])= (415) eV, ([8])= (833) eV

• 33S(n,elas)= 33S(n,tot)[8]-33S(n,)[5]; 33S(n,elas) is the highest possible with the data available, so the probability of losing energy for the neutron is also maximum being the probability of alpha emission minimum (conservative).

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Monte Carlo Simulations: Porras Phys. Med. Biol. 53 (2008) • Neutron point-like source with energy 13.5 keV & 24 keV (resonances).• Homogeneous medium (water) except a shell with 33S. • 33S(n,), conservative value: = (415) eV (Wagemans et al). = (833) eV (Coddens et al)

• Multidisciplinary research: nuclear physics, boron chemistry and nano technology.

• At En=13.5 keV E3.1 MeV, LET250 keV/m and x15m.

Javier Praena, CNA-Universidad de Sevilla, España

• With the conservative values of the it should be possible to deliver enough dose.

• The concentration of 33S and/or the neutron fluence could be decrease with the n_TOF experiment.

Motivations:33S as cooperative target in NCT

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FINAL METHOD: external heating of the chamber, Kapton (60 C), I=70 A. Person in charge: Wil Vollenberg – Vacuum Surface Coatings (CERN)In case of 33S it was evaporated 15 mg (75 m/cm2, thick) and 5 mg (25 m/cm2, thin)Conditions: 1 h vacuum pump, 2 h heating of Kapton and chamber, 5 min 70 A for S 1 h keeping on the temperature after coating.

Heating tape

Heated Kapton sampleWith thin Cu film

With thin CuSHeating tape

Test 2011: natS and 33S samples


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Rutherford Backscattering conditions:- Alpha beam. 3.5 MeV. ++He.- Backscattered alphas detected at 165 degrees.

Sample characterization at Centro Nacional de Aceleradores

Cu not reacting with 33S

Cu of the 33SCu compound33S (“thin”)

n_TOF Meeting June 2014 - Javier Praena – 33S(n,α)

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As boron is not a naturally present element in biomolecules, it has to be attached to certain compounds that tumor cells can absorbe in a larger quantity than normal ones. This is the case of the compound Boron-phenyl-alanine (BPA), which is the only compound used in the most recent clinical trials. This compound have been observed to accumulate in tumors with ratios tumor/normal tissue of 3.5, on average. The concentrations reached inside the cells are small, of the order of 10-20 microg/g of tissue (ppm). In spite of this fact, recent clinical trials, specially those performed in Finland and Japan, have produced very encouraging results for tumors of very bas prognosis (and for which other there are no other adequate treatments) as Glioblastoma Multiforme, the deadliest brain cancer, and recurrent Head and Neck cancers.

The fact that the cross section of 33S(n,alpha) is expected to be much smaller than for Boron could be compensated by means of a larger cell uptake and tumor selectivity.Sulfur is an essential element in the cell methabolism, and due to the enhanced reproductive ability of tumor cells, it is a good candidate by targeting them by means of sulfur aminoacids as cystine, which is a key compound in the synthesis of Glutathione, a biological process that is required for the growth of tissues. There are in vitro studies of cystine uptake by T-cell tumor lines which show sulfur concentrations of the order of mg/g (ppt), even when the cystine is added to the culture medium at a level in the physiological range [1]. Another example is Thiouracil that has observed to be uptaken by melanoma cells because it binds to the precursors of melamine and not to the preformed melamine. There have been found in malignant cells concentrations of Thiouracil 50 times greater than those in normal cells [2]. In addition to this, sulfur is present in different peptides and proteins of important biological roles and in nanoparticles [3] with adequate features for passive tumor targeting via the enhanced permeation and retention effect (EPR) on tumors.

[1] PW Gout, YJ Kang, DJ Buckley, N Bruchovsky and AR Buckley, Increased cystine uptake capability associated with malignant progression of Nb2 lymphoma cells, Leukemia 11, 1329–1337 (1997).[2] JA Coderre, S Packer, RG Fairchild, D Greenberg, B Laster, P Micca and I Fand, Iodothiouracil as a melanoma localizing agent. J Nucl Med. 27, 157-64 (1986).[3] R Tenne, Inorganic Nanotubes and Fullerene-Like Materials, Nature Nanotechnology 1, 103-111 (2006).

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For the p-isotopes nucleosynthesis the calculations with Hauser Feshbach Statistical Models to reproduce the solar abundances disagree in more than a factor of 2 in case of neutron- and proton-induced cross sections.

For alpha-induced cross sections the discrepancies between solar abundances experimental data and calculations are much larger that 2 (-nucleus potential).

Experimental efforts: measured data for testing and improving HFSM calculations.[At. Dat. Nucl. Dat. Tab. 75, 1 (2000)], [At. Dat. Nucl. Dat. Tab. 79, 47 (2001)]

The p-process: 32 proton-rich stable isotopes cannot be formed in neutron capture scenarios.Candidate: SN-II, sequences of (,x) and -decay.


Motivations: (n,) data for HFSM

1 Proposal to the ISOLDE and Neutron Time-of-Flight Committee 33 S(n,α) 30 Si cross section...

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