Beam energy optimization for Mu2e @ PIP-II Vitaly Pronskikh, Doug Glenzinski, Kyle Knopfel, Nikolai Mokhov, Robert Tschirhart Fermi National Accelerator Laboratory November 13, 2015 Particle Accelerator for Science and Innovation, Fermilab, Batavia
Introduction • An improved proton source will be required for a next generation Mu2e • Necessary to understand: – Expected muon yield and muon stopping rates as a function of proton energy – Potential performance constraints as a function of proton beam energy • MARS15 is used because the energy-deposition-related quantities are well modeled as well as DPA damage (displacement-per-atom) • PIP-II : Mu2e upgrade potential (@800 MeV) > 100 kW (linac), 120 kW (@8 GeV) (Booster), energies within the range were also considered • The energy range studied: 0.5 GeV – 8 GeV. 2 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Baseline Mu2e and MARS15 simulations • 8 GeV 8 kW proton beam • W target L=16 cm D=0.6 cm PS (beam σ =0.1 cm) • Bronze HRS (tungsten TS considered for upgrade), CDR design is used for the study STT • PS, TS, DS (17-foil Al stopping DS target (STT)) • In MARS15 simulations: DPA and power density vs beam energy LAQGSM, thresholds: 1E-12 vs HRS material GeV for neutrons, 100 keV for Muon yield/stopping rate vs beam energy Figure of merit (stopping rate per DPA) charged h., muons, photons 3 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
DPA limit and model Total DPA Neutron-induced DPA HRS: Bronze, Tungsten DPA model: NRT (below 20 (150) MeV ENDFB-VII/NJOY based cross section library FermiDPA 1.0) is used. NbTi coils DPA limits incorporate KUR measured data 4-6E-5 DPA 4 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Power density (PD) and other limits Power density limit: -depends on the cooling scheme -involves many other assumptions Dynamic heat load limit: -scales with the number of cooling stations Absorbed dose limit: usually high DPA, 10 -5 Power Quantity Absorbed Dynamic density, dose, heat load, µW/g MGy/yr W Specs 4-6 30 0.35 100 5 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
DPA as a function of beam energy Bronze absorber Tungsten absorber -6 -3 7.0x10 3.0x10 -6 -4 1.8x10 5.0x10 -3 2.8x10 beam power 1 kW DPA/Tp, yr -1 GeV -1 -3 2.6x10 beam power 1 kW PD/Tp, mW/g/GeV DPA/Tp, yr -1 GeV -1 -6 -6 1.6x10 6.0x10 PD/Tp, mW/g/GeV -4 -3 4.0x10 2.4x10 -3 2.2x10 -6 1.4x10 -6 -3 5.0x10 2.0x10 -4 3.0x10 -3 1.8x10 -6 1.2x10 -3 1.6x10 -6 4.0x10 -4 2.0x10 -3 DPA 1.4x10 -6 1.0x10 DPA Power density -3 1.2x10 Power density -6 -3 3.0x10 1.0x10 -7 -4 8.0x10 1.0x10 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Tp, GeV Tp, GeV DPA damage and peak power density are: Largest at ~3 GeV and drops with energy below that energy Larger for bronze than for tungsten by a factor of ~3-4 6 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
DPA and power density @ 100 kW 100 kW beam power 100 kW beam power -1 -4 2.4x10 8x10 -1 2.2x10 -4 7x10 Power density, mW/g -1 2.0x10 -1 1.8x10 -4 6x10 -1 -1 1.6x10 DPA, yr -4 5x10 -1 1.4x10 -1 Bronze HRS 1.2x10 -4 4x10 -1 Tungsten HRS 1.0x10 -4 Bronze HRS 3x10 -2 8.0x10 Tungsten HRS -2 6.0x10 -4 2x10 -2 4.0x10 -4 1x10 -2 2.0x10 0.0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Tp, GeV Tp, GeV • DPA: Current coil design can likely tolerate 100 kW at proton energies < 1 GeV (if HRS thickness is increased). • Power density: current coil design/cooling scheme can tolerate 100 kW at Ep = 0.8 GeV and lower. For higher energies another cooling scheme may be required. • Above 1 GeV (DPA) or 2 GeV almost flat with energy. 7 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Mu- spectra and yields at TS Mu- momentum spectra at TS -1 10 1.E-04 0 50 100 1.E-05 per proton 1.E-06 -2 10 1.E-07 N 1.E-08 -3 10 1.E-09 - entering TS 1.E-10 -4 10 1.E-11 0 1 2 3 4 5 6 7 8 9 p, MeV/c Tp, GeV 0.5 GeV 3 GeV 8 GeV Constant beam intensity (not power) = 6 · 10 12 p/s Steepest rise in µ − yields is between 0.5 and 2 GeV. Effective flux-based approach was used for counting muons 8 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Acceptance Fraction that stops in the Al target Fraction that stops in the Al target Mu- momentum at entrance to TS (MeV/c) Mu- momentum at entrance to TS (MeV/c) At 0.8 GeV Average 1-8 GeV Calculated using G4beamline, used with MARS15 calculated muon spectra at TS 9 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Mu- stopping rates and Figure of Merit - stops, 3yr @ 100 kW 19 4x10 - /DPA) 19 3x10 - stopped FOM (stopped 1E22 19 2x10 19 1x10 Bronze HRS Tungsten HRS 1E21 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Tp, GeV Tp, GeV • 3 years = 4.7E21 protons on target @ 8 GeV (4.7E22 @ 0.8 GeV) • If only stopped muons are considered: 2-3 GeV • If DPA is also considered: 1-3 GeV • The FOM for 0.8 GeV is about the same as it is for 8 GeV 10 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Single-event sensitivity and limiting beam power R ses , 3yr@100 kW 8.0x10 -18 • The single-event-sensitivity (SES) corresponds to the rate of -to-e 6.0x10 -18 conversion at which the experiment R ses would observe 1 event 4.0x10 -18 Current Mu2e R ses =3·10 -17 2.0x10 -18 • Estimated SES as a function of 0.0 0 1 2 3 4 5 6 7 8 9 proton beam energy Tp, GeV • Estimate is made assuming - 3y run at 100 kW (same timing structure, but increased duty factor) - Aluminum stopping target (ie. unchanged) Total number of stopped muons as on page 10 - Detectors can be made to handle increased rates so that acceptance and - resolution comparable to current estimates • Could achieve >x10 improvement for Tp in 0.8 – 5 GeV range 11 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Future plans Inner bore radius=20 cm No yield drop for R>17 cm Investigate the DPA and Power density deposition for a tungsten HRS with a reduced inner bore 12 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Conclusions • Energy dependence of DPA damage, power density, muon yield and muon stopping rate is studied. • A Figure of Merit is proposed: the ratio of stopped muon rate to DPA – FOM is largest in the 1-3 GeV range – FOM for 0.8 GeV is comparable to 8 GeV • Assuming detectors can be made to handle increased rates, can plausibly achieve x10 improvement in sensitivity for 100 kW at Tp = 0.8-5 GeV • Additional work required to understand whether current coil + tungsten HRS design can likely tolerate 100 kW 13 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 11/12/2015
Spare slides 14 Presenter | Presentation Title 11/11/2015
Mu- entering TS Ep, GeV Mu-/proton Stat. uncertainty Stat. uncertainty, % 0.5 4.45E-04 5.17E-06 1.2 0.6 9.26E-04 3.96E-05 4.3 0.7 1.51E-03 9.53E-06 0.6 0.8 2.20E-03 5.51E-05 2.5 0.9 2.83E-03 1.31E-05 0.5 1 3.55E-03 7.06E-05 2.0 2 9.57E-03 1.16E-04 1.2 3 1.47E-02 1.44E-04 1.0 4 1.34E-02 1.38E-04 1.0 5 1.58E-02 1.50E-04 0.9 6 1.85E-02 1.93E-04 1.0 7 2.06E-02 2.83E-04 1.4 8 2.25E-02 2.51E-04 1.1 15 Presenter | Presentation Title 11/11/2015
Mu2e@PIP-II upgrade plans Performance Parameter PIP PIP-II Linac Beam Energy 400 800 MeV Linac Beam Current 25 2 mA Linac Beam Pulse Length 0.03 0.5 msec Linac Pulse Repetition Rate 15 15 Hz Linac Beam Power to Booster 4 13 kW Linac Beam Power Capability (@>10% • Early next decade 4 ~200 kW Duty Factor) • 250 meter linac (20 Mu2e Upgrade Potential (800 MeV) NA >100 kW Hz)? 4.2×10 12 6.4×10 12 Booster Protons per Pulse • 800 MeV proton beam Booster Pulse Repetition Rate 15 15 Hz (2 mA) Booster Beam Power @ 8 GeV 80 120 kW Beam Power to 8 GeV Program (max) 32 40 kW • -> Booster -> 8 GeV Main Injector Cycle Time @ 120 GeV 1.33 1.2 sec (120 kW) LBNF Beam Power @ 120 GeV* 0.7 1.2 MW • -> Main LBNF Upgrade Potential @ 60-120 NA >2 MW Injector/Recycler GeV • ->120 GeV (1.2 MW) Table from S.Holmes, Neutrino Summit, 2014 16 Vitaly Pronskikh | Energy dependence of DPA damage in SC coils 11/11/2015
17 Presenter | Presentation Title 11/11/2015
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