Status of the. B and Li production experiments at LNL

Transcription

1 Status of the B and Li production experiments at LNL V.L. Kravchuk1, E. Wildner2, M. Cinausero1, G. De Angelis1, F. Gramegna1, T. Marchi1, G. Prete1, E. Benedetto2, C. Hansen2, G. Collazuol, M. Mezzetto, G. Derosa4, V. Palladino4, E. Vardaci4 Laboratori Nazionali di Legnaro, Legnaro (PD), Italy 2 CERN, Geneve, Switzerland Dipartimento di Fisica, Universita di Padova and INFN sezione di Padova, Padova, Italy 4 Dipartimento di Fisica, Universita di Napoli and INFN sezione di Napoli, Napoli, Italy 1

2 Overview Introduction B production Proposal of a measurement at LNL (V.L. Kravchuk et al) - Cross section and Angular distribution - Theoretical calculations - Experimental set-up - Conclusions (proposal dead-line) Li production Status of data analysis (E. Vardaci et al)

3 Introduction B and Li are interesting source of relatively high-energy neutrinos via beta decay: 5 B 4 Li Be e e Be e e τ ~ 0.77s τ ~ 0.4s Rubbia et al propose (NIM A5 (200) 475) the following production reactions: (1) Li 2 He (2) 7 Li 21 H 5 B n Li p Optimal energies might be: 1) ~20 MeV for Li ions on He target (equivalent to ~10 MeV for He on Litarget) 2) ~25 MeV for 7Li ions on D target (equivalent to ~ MeV for D on 7Li target)

4 Main questions about Li 2 He 7 Li 1 H 2 5 B n Li p 1) Magnitude of the integrated cross sections? and even more important 2) Angular distributions of radioactive ion in the final state?

5 B production Li(He,n)B Phys Rev C11 (1975) 70 Cross-section measurement We aim to increase significantly the precision of the crosssection with respect to the existing data (~0%) but what precision is required for the BETA BEAM project? Previous measurements of integrated cross-section: - 4 different experiments - positron counting technique (from B decay)

6 Li(He,n)B Angular distribution measurement The angular distribution is crucial for the BETA BEAM design study Nucl Phys A10 (197) 474 Angular distribution measurements were made only up to E(He)=5.7 MeV (neutron time-of-filght technique) Not easy to compare with total cross-section measurements

7 Li(He,n)B Figure 1. Differential cross section calculations for E=5. MeV are presented together with the experimental data (Nucl Phys A10 (197) 474). Different renormalized LSJ-components and the sum are shown. Theoretical calculations Figure 2. Differential cross section calculations for E=10 MeV (blue) and E=5. MeV (black) are shown together with the experimental data at E=5. MeV. The experimental errors vary from 10 to 0%. Theoretical calculations performed (V.L.Kravchuk) in collaboration with prof. S.A.Goncharov (Theor. dep. Moscow State University) Code DWUCK4 using zero range distorted wave born approximation (ZR-DWBA)

8 Li(He,n)B Proposed Experimental set-up at LNL-INFN (Italy) Technique: - counting neutrons with a time of flight (ToF) apparatus Beam: - He at 10MeV from LNL CN Van der Graaf - 2ns pulses, O(%) duty cycle Target: - O(100µg/cm2) thin metallic Li target Detectors: - liquid scintillator (n/γ pulse shape discrimination) - detectors located at proper angles - ToF over 2m distance from target CN can accelerate He beam up to an energy of 12 MeV (pulsed 2 ns) The high cost of He is an issue!!! Need ~ 0.25l at 15 bar keuro Currently we are pursuing 2 opportunities: a) Option LNL-Padova b) Option France?

9 RipeN Rivelatori per LNL Cylindrical Liquid Scintillators (BC501) (active scint. vol. 12.7cm diameter x 12.7cm height) Readout electronics: waveform digitizers (1GSs with 12bit resolution) pulse shape discrimination at low threshold - Some (7) RIPEN detectors will be located: at forward angles (5) + backward angles (1) + symmetric position (1) for beam centering - Distance from target ~2m - Efficiencies: well known, check with D(d,n)He reaction - n/γ PSD algorithms calibrated with radiactive sources

10 Li(He,n)B Li targets available at LNL - Target metallic Li (99.9%) deposited on backing (Upilex) ~0μm/cm2 thickness ~100μg/cm2 placed between two layers of carbon ~15μg/cm2 each target diameter ~cm Complementary measurements foreseen: - empty target runs backgroung from Carbon and Upilex - to estimate background from 1O contamination on target (if relevant) Example of ToF spectrum. From Nuovo Cim. 7 (197) 49 with similar experimental conditions (but worse resolution) and EHe=5MeV O and 12C backgroung strongly dependent on angle 1

11 Li(He,n)B CN proposal: BETABEAM B PRODUCTION MEASUREMENT FOR THE FP7 BETA BEAM DESIGN STUDY V.L. Kravchuk1, E. Wildner2, M. Cinausero1, G. De Angelis1, F. Gramegna1, T. Marchi1, G. Prete1, E. Benedetto2, C. Hansen2, G. Collazuol, M. Mezzetto, G. Derosa4, V. Palladino4, E. Vardaci4 FOR THE EUROnu WP4 COLLABORATION Laboratori Nazionali di Legnaro, Legnaro (PD), Italy 2 CERN, Geneve, Switzerland Dipartimento di Fisica, Universita di Padova and INFN sezione di Padova, Padova, Italy 4 Dipartimento di Fisica, Universita di Napoli and INFN sezione di Napoli, Napoli, Italy 1 Spokesperson: V.L. Kravchuk - kravchuk@lnl.infn.it Spokesperson: E. Wildner - Elena.Wildner@cern.ch Abstract We propose to study the reaction Li(He,n)B at the bombarding energy of 10 MeV. Accurate measurements of cross section and angular distribution of B production are necessary for the FP7 Design Study in progress of a neutrino beta beam based on a new storage/decay ring for ions accelerated in the CERN PS and SPS. The energies of neutrino from high Q B parents, in particular, match well the CERN-LN GS baseline. The 10 MeV pulsed (2 ns) He beam produced by the CN Van de Graaff accelerator will hit a 100 μg/cm2 Li target deposited on a 0 μm Upilex backing between two layers of Carbon (each 15 μg/cm2 thick). Seven liquid BC501 scintillation detectors of RIPEN array will be used for the detection of the recoil neutrons in the angular range from 0 to 90 degrees. To completely perform this experimental program one week is required by the CN coordinator for the He beam tuning. One week will be necessary to collect statistics in order to achieve the required 10% precision in the cross section and angular distribution measurements. Finally, another week will be needed for the background measurement with the bombarding energy of 10 MeV and for the cross check with the available data by measuring couple of days with the lower beam energy of 5 MeV.

12 Li(He,n)B Time scale We prepared proposal for a winter PAC/USP of Laboratori Nazionali di Legnaro. DEADLINE FOR THE PROPOSAL SUBMISSION: 2 JANUARY 2011 PAC/USP MEETING FOR PROPOSAL DEFENSE: -4 MARCH 2011 RESULTS OF THE PAC/USP EVALUATION: MID MARCH 2011 EXPERIMENT: WEEKS SPRING 2011 ( HOURS PER DAY) 1 WEEK: CN BEAM TUNING 2 WEEK: MEASUREMENT PHYSICS (10 MeV) WEEK: MEASUREMENT BACKGROUND + MEASUREMENT PHYSICS (5 MeV)

13 Li production 7 Li + D Li + p Status: - Data taking completed - Analysis on-going (E.Vardaci, M.Cinausero, et al) Technique: proton measurement with charged particle spectrometer Beam: 7 Target: CD2 target Detectors: Li at 25MeV from LNL XTU tandem (pulsed beam) Experimental apparatus πlp E- E (Si-CsI:Tl) telescope Er E- E technique Ε Er PSD technique Ε

14 Proton energy spectrum Li (25MeV) + H --> Li + H E1 E2 E E4 12 H E Lab (MeV) Li(D,p)Li ThetaLab

15 7 Li(D,p)Li Proton angular distribution Preliminary Li (25MeV) + H --> Li + H H Lab Angle d σ /d Ω (arb. units) Li (25MeV) + H --> Li + p ThetaLab Li Lab Angle Conclusions - Angular distributions analysis: errors need to be quantified - Might be interesting compare with theoretical calculations - Integral cross sections not as straightforward: normalization to be addressed

16 Additional material

17 4. DIRECT OR REVERSE KINEMATICS? D. Neuffer, Nucl. Instr. and Meth. A 55 (200) LISE++ Kinematics Calculations 1) MeV He (1 MeV Li) intermediate case; 2) 10 MeV He (20 MeV Li) optimum energy according to the articles of Rubbia et al. and Neuffer; ) 5.5 MeV He (11 MeV Li) energy with the maximum reaction cross-section from the data in literature. The projectile He energy will be 10 MeV. We plan also to measure another point at 5 MeV. For each of the energy cases described above 4 calculations were performed: two-body direct kinematics He + Li -> B + 1n; elastic scattering direct kinematics He + Li -> He + Li; two-body reverse kinematics Li + He -> B + 1n; elastic scattering reverse kinematics Li + He -> Li + He.

18 neutron/γ discrimination with liquid scintillators pulse shape Old digital electronics at RIPEN (better resolution obtained with new electronics) Total ToF γ n γ n fast vs slow signals γ -gated ToF n-gated ToF γ n n γ

19 πlp layout

20 Li + D Li + p analysis 7 E- E discrimination time- E PSD discrimination

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