Beam energy optimization for Mu2e @ PIP-II Vitaly Pronskikh, Doug - - PowerPoint PPT Presentation

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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,

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SLIDE 1

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

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SLIDE 2

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.

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II 2

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SLIDE 3

Baseline Mu2e and MARS15 simulations

  • 8 GeV 8 kW proton beam
  • W target L=16 cm D=0.6 cm

(beam σ=0.1 cm)

  • Bronze HRS (tungsten

considered for upgrade), CDR design is used for the study

  • PS, TS, DS (17-foil Al stopping

target (STT))

  • In MARS15 simulations:

LAQGSM, thresholds: 1E-12 GeV for neutrons, 100 keV for charged h., muons, photons

3

DPA and power density vs beam energy vs HRS material Muon yield/stopping rate vs beam energy Figure of merit (stopping rate per DPA)

PS TS DS STT

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 4

DPA limit and model

4

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 Neutron-induced DPA Total DPA

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 5

Power density (PD) and other limits

5

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

Quantity DPA, 10-5 Power density, µW/g Absorbed dose, MGy/yr Dynamic heat load, W Specs 4-6 30 0.35 100

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 6

DPA as a function of beam energy

6

1 2 3 4 5 6 7 8 9 3.0x10

  • 6

4.0x10

  • 6

5.0x10

  • 6

6.0x10

  • 6

7.0x10

  • 6

beam power 1 kW DPA/Tp, yr-1 GeV-1

DPA Power density Tp, GeV

Bronze absorber

1.0x10

  • 3

1.2x10

  • 3

1.4x10

  • 3

1.6x10

  • 3

1.8x10

  • 3

2.0x10

  • 3

2.2x10

  • 3

2.4x10

  • 3

2.6x10

  • 3

2.8x10

  • 3

3.0x10

  • 3

PD/Tp, mW/g/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

1 2 3 4 5 6 7 8 9 8.0x10

  • 7

1.0x10

  • 6

1.2x10

  • 6

1.4x10

  • 6

1.6x10

  • 6

1.8x10

  • 6

beam power 1 kW DPA/Tp, yr-1 GeV-1

DPA Power density Tp, GeV

Tungsten absorber

1.0x10

  • 4

2.0x10

  • 4

3.0x10

  • 4

4.0x10

  • 4

5.0x10

  • 4

PD/Tp, mW/g/GeV 11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 7

DPA and power density @ 100 kW

  • 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 1 2 3 4 5 6 7 8 9

1x10

  • 4

2x10

  • 4

3x10

  • 4

4x10

  • 4

5x10

  • 4

6x10

  • 4

7x10

  • 4

8x10

  • 4

Bronze HRS Tungsten HRS

DPA, yr

  • 1

Tp, GeV

100 kW beam power

1 2 3 4 5 6 7 8 9 0.0 2.0x10

  • 2

4.0x10

  • 2

6.0x10

  • 2

8.0x10

  • 2

1.0x10

  • 1

1.2x10

  • 1

1.4x10

  • 1

1.6x10

  • 1

1.8x10

  • 1

2.0x10

  • 1

2.2x10

  • 1

2.4x10

  • 1

Bronze HRS Tungsten HRS

Power density, mW/g

Tp, GeV

100 kW beam power

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 8

Mu- spectra and yields at TS

8

1.E-11 1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04

50 100

N

p, MeV/c Mu- momentum spectra at TS

0.5 GeV 3 GeV 8 GeV

Constant beam intensity (not power) = 6 · 1012 p/s Steepest rise in µ− yields is between 0.5 and 2 GeV. Effective flux-based approach was used for counting muons

1 2 3 4 5 6 7 8 9 10

  • 4

10

  • 3

10

  • 2

10

  • 1

 per proton

Tp, GeV - entering TS

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 9

Acceptance

At 0.8 GeV Average 1-8 GeV Calculated using G4beamline, used with MARS15 calculated muon spectra at TS

9

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)

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 10

Mu- stopping rates and Figure of Merit

  • 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 1 2 3 4 5 6 7 8 9 1x10

19

2x10

19

3x10

19

4x10

19

stopped 

  • Tp, GeV

- stops, 3yr @ 100 kW

1 2 3 4 5 6 7 8 9 1E21 1E22

Bronze HRS Tungsten HRS

FOM (stopped 

  • /DPA)

Tp, GeV

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 11

Single-event sensitivity and limiting beam power

11 1 2 3 4 5 6 7 8 9 0.0 2.0x10-18 4.0x10-18 6.0x10-18 8.0x10-18

Rses Tp, GeV Rses, 3yr@100 kW

  • 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
  • The single-event-sensitivity (SES)

corresponds to the rate of -to-e conversion at which the experiment would observe 1 event Current Mu2e Rses=3·10-17

  • Estimated SES as a function of

proton beam energy

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 12

Future plans

12

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

11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 13

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 11/12/2015 Vitaly Pronskikh | Beam energy optimization for Mu2e @ PIP-II

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SLIDE 14

Spare slides

11/11/2015 Presenter | Presentation Title 14

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SLIDE 15

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

11/11/2015 Presenter | Presentation Title 15

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SLIDE 16

Mu2e@PIP-II upgrade plans

  • Early next decade
  • 250 meter linac (20

Hz)?

  • 800 MeV proton beam

(2 mA)

  • > Booster -> 8 GeV

(120 kW)

  • > Main

Injector/Recycler

  • >120 GeV (1.2 MW)

11/11/2015 16 Vitaly Pronskikh | Energy dependence of DPA damage in SC coils

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% Duty Factor) 4 ~200 kW Mu2e Upgrade Potential (800 MeV) NA >100 kW Booster Protons per Pulse 4.2×1012 6.4×1012 Booster Pulse Repetition Rate 15 15 Hz Booster Beam Power @ 8 GeV 80 120 kW Beam Power to 8 GeV Program (max) 32 40 kW Main Injector Cycle Time @ 120 GeV 1.33 1.2 sec LBNF Beam Power @ 120 GeV* 0.7 1.2 MW LBNF Upgrade Potential @ 60-120 GeV NA >2 MW

Table from S.Holmes, Neutrino Summit, 2014

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SLIDE 17

11/11/2015 Presenter | Presentation Title 17