Status on cold muonium production and testbeam request

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1 Status on cold muonium production and testbeam request A. Antognini 1,2, P. Crivelli 1, K. Kirch 1,2, D. Taqqu 1 M. Bartkowiak 2, A. Knecht 2, A. Papa 2, N. Ritjoho 2, D. Rousso 2, R. Scheuermann 2, A. Soter 2, M. De Volder 3, D. M. Kaplan 4 and T. J. Phillips 4 µ + 1 Institute for Particle Physics and Astrophysics, ETH Zurich, 8093 Zurich, Switzerland 2 Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland 3 Department Of Engineering, University of Cambridge, UK 4 Illinois Institute of Technology, Chicago, IL USA

2 onium, a precision tool in atomic physics µ + onium () hydrogen-like exotic atom pure leptonic system (1st and 2nd gen.) no finite size / nuclear effects 2

3 onium, a precision tool in atomic physics µ + onium () hydrogen-like exotic atom pure leptonic system (1st and 2nd gen.) no finite size / nuclear effects 1s-2s and HFS spectroscopy test of bound-state QED fundamental constants: m μ, R, m μ /m p, q μ /q e fundamental symmetries onium - antimuonium put limits on the charged lepton number violation 2

4 onium, a precision tool in atomic physics µ + onium () hydrogen-like exotic atom pure leptonic system (1st and 2nd gen.) no finite size / nuclear effects 1s-2s and HFS spectroscopy test of bound-state QED fundamental constants: m μ, R, m μ /m p, q μ /q e fundamental symmetries onium - antimuonium put limits on the charged lepton number violation gravity experiment? μ+ : elementary antiparticle from the second generation complementary to the composite antimatter (antihydrogen) gravity CERN unique possibility to compare gravity (test weak eq.princ.) in lepton generations 2

5 onium, a precision tool in atomic physics µ + onium () hydrogen-like exotic atom pure leptonic system (1st and 2nd gen.) no finite size / nuclear effects 1s-2s and HFS spectroscopy test of bound-state QED fundamental constants: m μ, R, m μ /m p, q μ /q e fundamental symmetries Statistics-limited partially by the source onium - antimuonium put limits on the charged lepton number violation gravity experiment? μ+ : elementary antiparticle from the second generation complementary to the composite antimatter (antihydrogen) gravity CERN unique possibility to compare gravity (test weak eq.princ.) in lepton generations 2

6 onium, a precision tool in atomic physics µ + onium () hydrogen-like exotic atom pure leptonic system (1st and 2nd gen.) no finite size / nuclear effects 1s-2s and HFS spectroscopy test of bound-state QED fundamental constants: m μ, R, m μ /m p, q μ /q e fundamental symmetries Statistics-limited partially by the source onium - antimuonium put limits on the charged lepton number violation gravity experiment? μ+ : elementary antiparticle from the second generation Not possible with present sources complementary to the composite antimatter (antihydrogen) gravity CERN unique possibility to compare gravity (test weak eq.princ.) in lepton generations 2

7 gravity: especially challenging Trajectory selection Measurement no gravity g x x with gravity Trajectory selection by collimation: large losses in atom number!

8 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 Increasing intensity: series of collimators = gratings. Effects of gravity: vertical shift in the periodic pattern of shadows If this effect is small, small grating period (d) needed Challenging: falls less than 1 nm during its few us flight! 4

9 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 5

10 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 g g 1 2 T 2 d C p N 5

11 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 g g 1 2 T 2 d C p N Interaction time ~ τ = few μs! 5

12 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 g g 1 2 T 2 d C p N Small grating period Interaction time ~ τ = few μs! 5

13 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 g g 1 2 T 2 d C p N Small grating period Interaction time ~ τ = few μs! Many atoms Large contrast N N 0 b 3 e (t D+T )/ C = A/A 0 5

14 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 E.g. to measure sign of g in ~2 days Using parameters d = 100 nm, T = 8 μs, N 0 = /s, C=0.3 6

15 gravity: especially challenging Gratings Detection d g 0 x A0 A no gravity with gravity x C = A/A 0 E.g. to measure sign of g in ~2 days Using parameters d = 100 nm, T = 8 μs, N 0 = /s, C=0.3 Present goals: beam development large flux (high N) small transverse momentum (high N, C) narrow energy distribution (high C) 6

16 State-of-the-art μ+ conversion SiO 2 Large (thermal) energy spread Broad angular distribution (~cosθ) 3-30 % conversion efficiency at T=296 K 7

17 State-of-the-art μ+ conversion Needed: a `cold source Low emittance, narrow energy distribution, large number SiO 2? Large (thermal) energy spread Broad angular distribution (~cosθ) 3-30 % conversion efficiency at T=296 K cooling conventional samples: almost no emission below 100 K (decreased velocities, and atoms sticking to the pore walls) 7

18 Proposal: production in superfluid helium (SFHe) From chemical potential E/k B ~270 K: atoms are ejected from bulk SFHe with v = 6.3 mm/μs vacuum The cold environment would ensure low thermal energy spread (~0.1 %), and narrow angular distribution (~30 mrad) SFHe 0.3 K PDF [arb. u.] from SFHe Thermal (296 K) Velocity [km/s] 8

19 Proposal: production in superfluid helium (SFHe) From chemical potential E/k B ~270 K: atoms are ejected from bulk SFHe with v = 6.3 mm/μs vacuum The cold environment would ensure low thermal energy spread (~0.1 %), and narrow angular distribution (~30 mrad) SFHe 0.3 K PDF [arb. u.] from SFHe Thermal (296 K) Velocity [km/s] Challenge: creating atoms close to the SFHe surface to minimize diffusion time / ensure high vacuum production rates 8

20 Cold production 1: thin SFHe He gas Large vacuum ejection can 4 MeV E be ensured by stopping lowenergy (~few kev) muons in a thin ~ 1 μm SFHe film B 10 kev ~1 μm SFHe ~50 nm Si 3 N 4 Reacceleration B-field extraction Electrostatic beamline 9

21 Cold production 1: thin SFHe He gas 4 MeV E ~1 μm SFHe B 10 kev ~50 nm Si 3 N 4 Reacceleration B-field extraction Electrostatic beamline The mucool PSI: cryogenic He gas target with complex E- fields and density gradients inside a 5 T solenoid B-field: ~10 kev beam with sub-mm (~100 μm) waist, 10-3 efficiency Compression: demonstrated. Vacuum extraction, reacceleration and B- field extraction needed 9

22 Cold production 2: delayed recombination ~100 μm SFHe E 7 mm/μs Conventional (surface / subsurface) muon beam bent vertically Broad stopping distribution in ~100 μm thick layer of SFHe Prompt recombination to is prevented by an external E field 4 MeV B Same E-field is drifting atoms to the surface, where they recombine with externally implanted electrons 10

23 Methods comparison Advantage Produces a pencil-beam of Disadvantage - requires special μ beam, expected 10-3 loss SFHe coated mirror SFHe E Conventional μ - relies on badly known physics / processes beam can be - needs extensive cold used instrumentation μ+ Need of an atomic mirror 11

24 Methods comparison Advantage Produces a pencil-beam of Disadvantage - requires special μ beam, expected 10-3 loss SFHe coated mirror SFHe E Conventional μ - relies on badly known physics / processes beam can be - needs extensive cold used instrumentation μ+ Need of an atomic mirror Proof-of-principle demonstrations needed: production in bulk SFHe at T < 0.5 K production prohibition with E fields Emission of from SFHe Reflection of from SFHe surfaces 11

25 Methods comparison Advantage Produces a pencil-beam of Disadvantage - requires special μ beam, expected 10-3 loss SFHe coated mirror SFHe E Conventional μ - relies on badly known physics / processes beam can be - needs extensive cold used instrumentation μ+ Need of an atomic mirror Proof-of-principle demonstrations needed: production in bulk SFHe at T < 0.5 K production prohibition with E fields Emission of from SFHe Reflection of from SFHe surfaces Dec

26 Methods comparison Advantage Produces a pencil-beam of Disadvantage - requires special μ beam, expected 10-3 loss SFHe coated mirror SFHe E Conventional μ - relies on badly known physics / processes beam can be - needs extensive cold used instrumentation μ+ Need of an atomic mirror Proof-of-principle demonstrations needed: production in bulk SFHe at T < 0.5 K production prohibition with E fields Emission of from SFHe Reflection of from SFHe surfaces Dec This year 11

27 SR Dolly, Dec (a) TOP 31 MeV/c D1 75 um Ti B SFHe E electrode insulator 1 mm D2 (b) Gas inlet Indium sealing HV feedthrough 10 mm Ti foil clamp Ag electrode detecting the precession of muon spin using e + from decay identifying by the appearance of a higher frequency component N(t) N 0 e t/ µ [1 + A µ (t) cos(! µ t)+a (t) cos(! t)]! 103! µ 12

28 Dec μsr measurement (raw data) Asymmetry (a) B= 50 G Empty target decay asymmetry in the silver electrode 0.15 Asymmetry Cell full Asymmetry Time (μs) 1 alpha asy phase field rate !! 0.2 (a) (b) 0.04 B= 50 G 0.15 B= 1.6 G Target filled with SFHe asymmetry 2 TFieldCos 3 fun1 simplexpo 5 fun1 = par4 * gamma_mu Asymmetry Time (μs) Time (µs) Disappearance of deltat_tdc_dolly_2765,h:2 /1,T0=1.20K,T1=1.76K,B=50.00G,E=??,Cell full signal musrfit: , 10:49:01, chisq = , NDF = 405, chisq/ndf = Time (μs) Appearance of signal 13

29 Preliminary results from μsr measurement (a) Relative decay asymmetry Region of interest Abela et al. JETP Letters 57, 157 (1993) 1 Present measurement Abela et al. Preliminary Temperature dependence of production efficiency: high (>70%) production rates were found at T=0.26 K Temperature [K] Electric field dependence of production rates: production can be prevented by applying fields of E~0.6 kv/cm Relative decay asymmetry Preliminary Voltage [V] 14

30 Next goal - extraction of from SFHe SFHe surface: A horizontal target Even for a test, we would need a special beam (vertically bent LEM, or surface muon beam) 15

31 Next goal - extraction of from SFHe SFHe surface: A horizontal target Even for a test, we would need a special beam (vertically bent LEM, or surface muon beam) If we don t bend the beam, can we bend the surface? SFHe is climbing (wetting) vertical walls easily But, a single SFHe film (few ~10 nm) has little stopping power 15

32 Next goal - extraction of from SFHe SFHe surface: A horizontal target Even for a test, we would need a special beam (vertically bent LEM, or surface muon beam) If we don t bend the beam, can we bend the surface? SFHe is climbing (wetting) vertical walls easily But, a single SFHe film (few ~10 nm) has little stopping power New concept: nanostructured targets coated with SFHe Large stopping power and surface area for escape SFHe film prevents atoms sticking to the wall e.g. coating mesoporous SiO 2 with SFHe? 15

33 Next goal - extraction of from SFHe SFHe surface: A horizontal target Even for a test, we would need a special beam (vertically bent LEM, or surface muon beam) If we don t bend the beam, can we bend the surface? SFHe is climbing (wetting) vertical walls easily But, a single SFHe film (few ~10 nm) has little stopping power New concept: nanostructured targets coated with SFHe Large stopping power and surface area for escape SFHe film prevents atoms sticking to the wall CNT forest (h ~ 500 um) Spatially ordered carbon nanotubes (CNT forests) carbon nanotubes (CNT) d~5 nm 15

34 The potential of SFHe coated CNT forests Single walled (monolayer) CNT SFHe film, ~5 atomic layer ~2 nm(first 1-2: not SF) SFHe film CNT 5 nm significant stopping power in SFHe vs carbon forest: ~5% graphite density, quasi-ordered structur fast escape? Si substrate 14 MeV/c 16

~5% graphite density, quasi-ordered structur fast escape?

35 The potential of SFHe coated CNT forests Single walled (monolayer) CNT SFHe film, ~5 atomic layer ~2 nm(first 1-2: not SF) SFHe film CNT 5 nm significant stopping power in SFHe vs carbon forest: ~5% graphite density, quasi-ordered structur fast escape? Si substrate 14 MeV/c And, the possibility for: Prefabricated holes for better extraction Free-standing structures for back-implantation 16

36 Testbeam plans 1 - room temperature tests Testing cryogenic detectors for beam characterization, using a known source Laser ablated silica aerogel, TRIUMF Start Scintillators Aerogel e + 17

37 Testbeam plans 1 - room temperature tests Testing cryogenic detectors for beam characterization, using a known source Laser ablated silica aerogel, TRIUMF Interferometer background estimation x e + e + x Start Scintillators Horizontal E-field, suppression of sample electron emission Aerogel HV - HV + Aerogel e + Start scint/ MCP e + 17

38 Testbeam plans 1 - room temperature tests Testing cryogenic detectors for beam characterization, using a known source Laser ablated silica aerogel, TRIUMF Interferometer background estimation x e + e + x Start Aerogel e + Scintillators Vertical E-field, possibility for spatial resolution Aerogel Start Scintillators HV + HV - e + 17

39 Testbeam plans 2 - cold target tests Entrance detector D2 0.3 K D1 Plastic scintillators 1.5 K SFHe coated target Targets with front implantation of 14 MeV/c beam emission measurement at room temperature emission at 0.3 K from a dry sample vs the one covered with SFHe Preliminary MC: > 1% conversion observable in ~1 h data taking (Rate: 25 khz) mean velocity (v ) & momentum distribution resolved by TOF data in two pairs of coincidence counters angular spread estimated with detectors segmented in the transverse direction # events # events Time [μs] D1 background decay D2 18

40 Impact of the 2018 testbeam Characterization of backgrounds for feasibility of a future interferometer experiment with mechanical gratings 19

41 Impact of the 2018 testbeam Characterization of backgrounds for feasibility of a future interferometer experiment with mechanical gratings Test of a new production target: carbon nanotube (CNT) forest 19

42 Impact of the 2018 testbeam Characterization of backgrounds for feasibility of a future interferometer experiment with mechanical gratings Test of a new production target: carbon nanotube (CNT) forest Emission of from SFHe coated nanostructured materials would prove: atoms can be ejected from the surface of SFHe atoms can reflect from SFHe surfaces 19

43 Impact of the 2018 testbeam Characterization of backgrounds for feasibility of a future interferometer experiment with mechanical gratings Test of a new production target: carbon nanotube (CNT) forest Emission of from SFHe coated nanostructured materials would prove: atoms can be ejected from the surface of SFHe atoms can reflect from SFHe surfaces + Bonus: large yield with narrow momentum distribution from the SFHe coated CNT forests might make them a useful cold (but diffuse) source 4 MeV SFHe coated porous material 19

44 Testbeam request for 2018 in πe1.2 area In total, 3 weeks of testbeam is requested in πe1.2 area, using MeV/c muons for the following tasks: Room temperature tests: cryogenic detectors, front and back μ+ implantation on aerogel target measurement with coincident μ+ and atomic e detection Background of detection by replacing target to μ+ dump 0.3 K measurements Cryogenic detector setup, with rotatable sample, front μ+ implantation in two targets (aerogel, CNT forest) Measurements of yield and beam characterization using warm, cold, and superfluid coated sampled Cryogenic target exchange, mounting of two other samples, and measurement Preferred time: December 2018 to accommodate cryogenic developments 20

45 Extra slide 1 - Inertial sensitivities Sensitivity [ g/g] N 0 =5e+03 N 0 =1e+04 N 0 =5e+04 N 0 =1e+05 Sensitivity [ g/g] C=0.1 C=0.2 C=0.3 C=0.4 C=0.3 N 0 = /s Measurement time [days] Measurement time [days] g 1 C p N 0 e (t D+T )/ d 2 1 T 2 d = 100 nm, 70% loss on grids, interaction time T = 8 μs Determining sign of g: 1-2 days with source of N 0 = /s, C=0.3 >100 days with N 0 = /s C=0.1 21

Extra 2 - Interferometry in near & far field 15. N= 3 X distance [slit spacing] 7.5 0-7.

the # of slits, N = A/d) X distance [slit spacing] -15. 7.5 0-7.

low-contrast transition region, ending up in the Fraunhofer fringes (far field) -15.

46 Extra 2 - Interferometry in near & far field 15. N= 3 X distance [slit spacing] Contrast of the Talbot-carpet (near-field) is lost in distances depending on the aperture A (or the # of slits, N = A/d) X distance [slit spacing] Talbot regime Transition: low contrast Fraunhofer regime Talbot region is followed by a low-contrast transition region, ending up in the Fraunhofer fringes (far field) -15. N = 9 X distance [slit spacing] Z distance [Talbot length] N = 21 The region of near and far field is influenced by the aperture size. 22

0-60. Talbot Low contrast Fraunhofer 0-1 -120. 0 2.8 5.6 8.4 11.

X distance [nm] 50. 0-50. -100 0 10. 20. 30. 40.

47 Extra 3 - near and far field with 120. Here A = 40 um (d=100 nm, N=400, L T = 17 um) +1 X distance [um] Talbot Low contrast Fraunhofer Z distance [mm] 100 Near field (Talbot) Fringes separable when X distance [nm] Z distance [um] L< 1 2 (N 1)L T L T = d2 (practically can be much smaller!) L> 2Ad (practically can be much larger!) 23

48 Extra 3 - effects of coherence length (CL) in aperture A Coherence length: base of this triangle CL=A CL=0.3 A CL=A, focusing CL=0.3 A, focusing 24

49 Extra 4: A high-contrast Mach-Zehnder setup Grating1 Grating2 Detector Far field Talbot regime Grids in effective far field, at least partial cpce on G1 25

The Muonium Antimatter Gravity Experiment Testing to see if something is the Matter with Gravity. Thomas Phillips IIT

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