R. S. Raghavan SNAC 11 September New Approach to the Search for Short Baseline Oscillations of ѵ e / ѷ e SNAC 11 Virginia Tech September R. S. Raghavan Virginia Tech With Sanjib Agarwalla, And the LENS Collaboration

R. S. Raghavan SNAC 11 September MeV ѵ e and ѷ e from Intense Radioactive Sources: Long Considered for Solar Neutrino Detectors PURPOSE: Neutrino Calibration of CC –Capture, Nu magnetic moment Search….. Remote Reactor Produced: 65Zn L. Alvarez (1973) 51Cr R. S. Raghavan (1978) 37Ar W. Haxton (1979) 90Sr G. Bellini & R. S. Raghavan (B’Xino Prpsl 1991) Se92 V. Kornoukov et al (2004) Ru99 M. Cribier et al (2011) On Site Accelerator produced (Protons) 8B Marrs et al (1973) 12N Adelberger et al (1993) The only sources made so far is 51Cr, 37Ar for Gallex, SAGE by remote Nuclear Reactors

R. S. Raghavan SNAC 11 September LENS-- 51Cr (CC nu capture in 115In) The first proposal to observe SB oscillation directly and explicitly. Dimensions of LENS (2-4m) tailored for contained waves for L/E~m/MeV MCi 51Cr for calibration part of LENS 2007—Apply the same experiment for Short Baseline Osc. Data on Sterile Osc. Essential for Precison Calibration of CC cross section Unique features : Unsurpassed Background Control Very high granularity  Sharp event localization Small souces  ΔL ~30 cm Grieb, Link, RSR PR D75, Cr in LENS 4x10 MCi

R. S. Raghavan SNAC 11 September ISSUES Very intense multiple MCi sources Remote Production—transportation  On-Site Source Production Background—Internal source  External Geometries Multiple sources for long lived cases-51Cr  Continuous on-site production Nue,Nuebar Sources, in same set up? Possible answers in present phase of Sterile LENS-program

R. S. Raghavan SNAC 11 September Primary Issue—Smaller Source Intensities? New Approach Electron scattering (ES) instead of CC capture in Indiun) (nuebar intrinsically more accessible, σ higher via IB) ES Practical only with Additional physical signature Possible ONLY with --Unique tool of LENS technology  kCi instead of MCi scale nu sources  Breakthrough ?

R. S. Raghavan SNAC 11 September Plan of Talk ES signature LENS Technology Background—Well known from BOREXINO Source Technology Possible sources and Reactions, Source Parameters Sensitivity estimates focused on “Reactor flux anomaly”

R. S. Raghavan SNAC 11 September Electron scattering Why ES? Target is electron –N tgt = x250 In115, σ = 0.1σ(CC) In115)   Signal rate ~25 times that of CC (nue+115In via 51Cr) Source intensity can be reduced by x25 using ES  Breakthrough? -- ONLY IF ES signal is taggable BUT No Intrinsic tag (except energy of ES signal) BOREXINO—solved by extraordinary PC purity, very massive shielding (6mwe) And ~3500 mwe cavity depth). IS THERE A SIMPLER WAY? How to Add physical signature to ES events—  Use highly granulated detector (~ 10^6g cells in 50 ton LENS detector– few cm cells)  Can discriminate SINGLE CELL event---( ES restricted to mm tracks) Overall Background from Alphas (single cell events BUT alpha discrimination from Pulse Shapes) Gammas (only multiple cell events in LS detector containing only C and H— --LENS without Indium shake down pre- phase of LENS before filling with In-LS) ES signal— can be mostly ONLY single cell events Key granularity available in a 100 ton scale detector --ONLY IN LENS  Breakthrough

R. S. Raghavan SNAC 11 September LENS Design Basic elements of LENS Solar Detector with Indium Delayed coincidence of Solar prompt and decay γ—Suppression -- 10^6 Single event spatial localization— 3x10^6 Total 10^12 --Sufficient to suppress Indium115 beta-decay background LENS Sterile nu detector  LENS Design at present  Cells 2.5x2.5x2.5 cm in 50 ton detector of LS 3.x3.5x3.5 m cube  3x10^6 optically independent cells available for discriminating ES single cell events from multicell background events

R. S. Raghavan SNAC 11 September

Dark Containment Electronics Tent Liquid Handeling System MicroLENS KURF  LENS MicroLENS Prototype in Scintillation Lattice Design constructed in Rm 10 at VT and deployed by truck in KURF

R. S. Raghavan SNAC 11 September LENS –Granular Detector Unit Cell 25x25x25 mm In-loaded Scint Blank Scin Buffer

R. S. Raghavan SNAC 11 September

TGT Tag Reactionσ(cm 2 )TechTag γ MeV Delay τ (μs) L max m εE th MeV p ṽ e p  e + n (τ) γ 6x10 MeV LS2.2~200~3.5~ In ν e 115 In  e Sn*(τ)2γ 3x10 MeV LENS ~ SourceMean Life (s) Prod. Reaction (MeV) Power (kW) Target Mass σ (mb) E(ν) (MeV) ν Source 6 He( ṽ e ) Be(n,α)DT on site generator 300 kg x Cr ( ν e )3.45x Cr(n,γ) ( n th ) 52Cr(n,2n) Nuc. Reactor DT on site n-generator 50kg 500 kg /10MCi /y Sources

R. S. Raghavan SNAC 11 September v Ѵ Fluence Eqvuivalent Activity Evts w/o Osc. Evts w. Osc. 51 Cr(ν e –In CC) 8.65x10 23 ~1 MCi Cr( ν e -e ES)6.98x10 22 ~70 kCi He( ṽ e, p) 4.12x10 21 ~4 kCi Rates for 3σ measurement of 3+2 osc model (T. Schwetz et al Talk at LNGS)

R. S. Raghavan SNAC 11 September Source Details 6 He: (100% beta: Endpt = 3.5 MeV; Tau =1.15 s) He production rate: (n,α) cross section = 0.1b 20 cm thick BeO blanket: S= 3.5x10 14 x x 1.44x10 24 x3.1x10 7 = 16x10 20 = 1.6x10 21 /y Thick blanket  50 cm –Rate = 12/1.44= 8.33 = 1.33x10 22 /y Thin Blanket rate = 1.5x10 21 Thick Blanket rate = 1.25x10 22 Maximum for n/s (LBNL) = x3, x3 (estimate from n2n multiplication  Neutrino rate ~ 1.25x10 23 /y N-multiplication due to (n,2n): In the dT reaction (14.1 MeV) hardly any neutrons are lost to n,2n because even after successive n,2n extra neutrons are produced and the neutron flux grows with enough energy to make the Be(n,α). Rough estimate, x3 enhancement n,2n N, n,α

R. S. Raghavan SNAC 11 September The single target coaxial neutron generator with dimensions of 26 cm in diameter and 28 cm in length is expected to generate a 2.4 MeV D-D neutron flux of 1.2 x or a 14 MeV D-T neutron flux of 3.5 x n/s. An adaptation of the coaxial generator design uses a versatile nested configuration with multiple plasma and target layers where ion beams can impinge on both sides of the targets to enhance neutron yield. A generator with this nested design and dimensions of 48 cm in diameter and 35 cm long should generate a neutron output 10 times higher than the single target generator described above. Thus, D-D neutron output higher than n/s and D-T neutron output of n/s should be attainable. A cylindrical neutron generator configured to approximately 20 cm in length. Compact Sources for 14 MeV n production: Info from LBNL website

R. S. Raghavan SNAC 11 September LENS Detector 4x4x4 m Fe wall of LENS chamber 30 cm W box for γ shield 20 cm thick Target Blanket BeO, Cr (nat) Compact neutron generator On-Site Production of Neutrino Source for SB Osc Search in LENS Tugsten Shield

R. S. Raghavan SNAC 11 September Experimental Specs LENS Detector: LS (PC no Indium)) 50 tons  3.5x3.3x3.5 molar (Shake down phase for Lens Solar —Source switched off --measure detector response (over detector volume), base background… External gammas (rock) shielding (steel 30 cm ( conceptual) Source assembly (conceptual) 40x40x40 cm Source distance (conceptual) 100 cm Energy gate for Cr ES keV (nu energy is monochromatic) Event localization: ΔL = 2.5 cm (fixed) Nu Reactions Nue (51Cr) ES nuebar+p  e+ +n (delay 200 μs (+p  2.2 MeV γ)

R. S. Raghavan SNAC 11 September Background—mainly ES bgd via SINGLE cell discrimination in LENS In unsegmented LS detector (Borexino) gamma events are observed calorimetrically—only energy and center of gravity of event is measured In a highy granular detector (LENS), in addition, the spatial distribution hits in the event art explicitly observed. Powerful new physics information on type of event, gamma-electron discrimination—application to tag ES events. Point like events are also made by alphas—discimination by pulse shapes (as in Borexino)

R. S. Raghavan SNAC 11 September Summary of single cell bgd events Gammas External bgd --single cell (photo fractions –only C and H in LS) band external shielding (much reduced compared to Borexino) 478 gammas from surface activity of 7Be Cosmic muons---Complete track observed Cosmic activity –C10, C11 (positron decay) Fast neutrorns (recoil protons) Slow neutrons (capture gammas) Betas Be7 solar neutrinos (in same window—unremovable) 210 Bi Possible 85Kr Rn by products from Rn emanation from materials Direct alphas Alpha pulse shape discrimintation

R. S. Raghavan SNAC 11 September Preliminary Background estimation Assume radiopurity – 10^-16 g/g (x10 Borexino) Other bgd guided by BOREXINO Solar neutrinos (scaled to 50 tons)+ impurities = y Source Signal for 51Cr = 5575/y (Bx Collaboration, PRL in Press)

R. S. Raghavan SNAC 11 September Fig. 1 Ratio of events with and without sterile oscillation as a function of the reconstructed L/E for Cr 51 (ν e, ES) and 6 He ( ṽ e, p) in 50 ton LS with the (3+2) best-fit parameters from ref. 18 Fig. 2 Expected constraints on sterile neutrinos in the (3+1) model 20 at 99% C.L. (2 dof) using P ee _ mode for 51 Cr (ν e ES) and 6 He ( ṽ e, p) sources. The total intensity used for 51 Cr is 5 x and for 6 He 2.5 x The dashed green curve shows the limit from reactor ṽ e data with new reactor fluxes 19. The triangle and the bullet show the (3+1) best-fit values of all reactor data with old and new fluxes respectively.

R. S. Raghavan SNAC 11 September Summary and Conclusions Low intensity –kCi scale nu Sources--Breakthrough Local on-site Production Nue and Nuebar Sources Tight Geometries– Small source extensions Relatively Inexpensive LENS-Solar not affected. New technology of highly granular 100 ton Scale detector Unique New tool Opens New Physics Probes- in addition to above  A LENS Program –not just an expeiment

R. S. Raghavan SNAC 11 September DEPTH—430m we LENS Program in INDIA?