Towards a first measurement of the free neutron bound beta decay - PowerPoint PPT Presentation

Towards a first measurement of the free neutron bound beta decay hydrogen atoms at a high flux beam reactor throughgoing beam tube E. Gutsmiedl 1 , W. Schott 1 , K. Bernert 1 , R. Engels 2 , T. Faestermann 1 , P. Fierlinger 3 , R. Gernhäuser 1 ,R. Hertenberger 4 , S. Huber 1 , I. Konorov 1 , B. Märkisch 1 , S. Paul 1 , C. Roick 1 , H. Saul 1 , S. Spasova 1 , T. Udem 5 , A. Ulrich 1 1 Physik-Department, Technische Universität München, D-85748 Garching, Germany 2 Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany 3 Excellence Cluster Universe, Technische Universität München, D-85748 Garching, Germany 4 Sektion Physik, Ludwig- Maximilian- Universität München, D-85748 Garching, Germany 5 Max- Planck- Institut für Quantenphysik, D-85748 Garching, Germany 1

Two- body neutron decay n → H + 𝜉 T H = 325.7 eV, β = 0.83 · 10 -3 , BR = 4 · 10 -6 Four hyperfine spin states exist (L. L. Nemenov, Sov. J. Nucl. Phys. 31, 115 (1980), L. L. Nemenov and A. A. Ovchinnikova, Sov. J. Nucl.Phys. 31, 659 (1980), W. Schott et al., Eur. Phys. J. A30, 603 (2006)) 83.2 % H(1s), 10.4 % H(2s) 2

Hyperfine spin states Configurations 1 – 3 within SM (H (𝜉) = 1), population probabilities (44.14 %, 55.24 %, 0.622 % for gS = gT = 0) given by Χ = (1 + gS) / ( λ - 2 gT), λ = gA / gV = -1.2761 (+14 − 17) (D. Mund, B. Märkisch, M. Deissenroth, J. Krempel, M. Schumann, H. Abele, A. Petoukhov, and T. Soldner, Phys. Rev. Lett. 110, 172502 – Published 23 April 2013) 3

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-0.0026 < g T / g A < 0.0024 (C.L. 95 %) (R. W. Pattie, Jr., et al. PRC 88, 048501 (2013) g S upper limit should be reduced by a factor 10 H ν should be measured within 10 -3 9

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Frm2 SR6 beam tube neutron and gamma flux T n < 0.6 eV, E γ < 0.5 MeV 11

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Ti-sapphire CO 2 14

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E = (1 – R) -1 ≈ 10 6 16

First step BOB monoenergetic H atoms are to be measured, e. g., at a throughgoing beamtube (PIK) using an Ar gas cell (H(2s) → H - , F. Roussel et. al., PRA 16, 1854 (1977)), electrostatic focusing elements, a pulsed electric deflector, a Bradbury Nielsen (BN) gate chopper and an MCP 17

PIK experimental setup 18

H(2s) + Ar → H - + Ar + cross section σ (T H(2s) = 0.33 keV) ≈ 5 · 10 -17 cm 2 19

Ar cell schematically 20

Electrostatic quadrupole doublet Φ 3 cm aperture 21

Pulsed electric deflector 2 cm x 4 cm aperture 22

Bradbury Nielsen gate chopper 23

ሶ ሶ ሶ Expected H - rate N H = BR ( ׬ 𝜚 𝑨 Ω 𝑨 𝑒𝑊 )/ (4π τ n v n ) = 2 𝑠 2 π z n ത = BR 𝜄 1 𝜚 / (2 τ n v n ) = 7.3 s -1 𝑡 with θ 1 = 0.14 (8 ° ), r s = 1.5 cm, z n = 0.5 m, ത 𝜚 = 10 14 cm -2 s -1 , ሶ N H(2s) = 0.73 s -1 p (l m = 0.176 m, σ = 5 · 10 -21 m 2 ) = 8.4 · 10 -3 mbar P (H(2s) → H - ) = n Ar σ Δz = 0.18, n Ar = 2 · 10 20 m -3 N H- = 0.13 s -1 P (H(2s) → H + ) = 0.45 (2 laser) N H+ = 0.33 s -1 24

N = 4.4 · 10 4 results ( ሶ N H+ = 0.33 s -1 ), i. e., 1.5 d measuring time 25

N = 8.3 · 10 5 results ( ሶ N H+ = 0.33 s -1 ), i. e., 29 d measuring time 26

Breit- Rabi diagram of the 2 S 1/2 2 P 1/2 hyperfine splitting 27

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W 4 W 4 obtained by measuring v ββ = N β1 -1 / N β00 v ββ = N 4 / (N 1 sin 2 θ + N 2 cos 2 θ) = = 2 N 4 / (N 1 + N 2 - cos2θ (N 1 - N 2 )) for B << B c , 2θ ≈ π/2, cos2θ ≈ 0 v ββ = 2 N 4 / (N 1 + N 2 ) → W 4 ≈ (1/2) v ββ for B large, cos2θ ≈ 1 v ββ = N 4 / N 2 30

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being 7.9 % of W 3 (≈ dW 3 ) background eliminated by ionizing these (n>2)s H atoms using a λ = 1.458 µm laser 32

Mockup setup W.Schott et al., MLL Annual Report 2014, 33

Cup H - current vs. spin filter magnet current 34

Cup current vs. counter field grid voltage 35

Differentiated D 36

Difference between 𝑈 𝐼− and T H H(2s): 𝑈 𝐼− = T H + 10.2 eV = = 335.9 eV dT H = E 0 β dv/c = 5.7 eV Δt / t = - ( 1/2) ΔT H / T H , t = 4 µs at s = 1m, Δt = 63 ns 37

A TOF spectrometer (BN gate chopper) • Technique: Use two electric grid systems (fast switchable) – Principle as for neutron chopper system – „ close “ means electric field „on“: deflecting H - or quenching of H(2s) – „ open “ means no field: H - or H(2s) survives passage • Operation of two gates spatially separated by 1m using fast HV pulsing technique – FPGA based fast logical system drives HV source – Generates pulse-pattern with variable pulse length („open“ time), delay time between the two electric systems and repetition rate – Typical rise time of HV pulse: 10ns – Typical gate time: 200-500ns – Typical driving voltage: 200-500V 38

BN Gate How the BN gates functions: • HV Typ = 250 V /grid (HV max = 500V) • use two grids intercalated in one plane • HV 1 = +250 V • HV 2 = -250 V Example: charged particles Gate open Gate closed 39

BN gate photo- etched grid Newcut 434 East Union St. Newark, NY 14513, USA 40

Grid dimensions (mil) α = π q U wire / (2T H- ln (1/ tan(π / (4a/r)))) = 22.3 °, U wire = ± 200 V, 2a = 43.5 mil, 2r = 5 mil 41

Pulse generation for BN gate grids DC/DC converter FET driver HV pulse generation FPGA signals +HV1 C7 GND1 DRV1 0.1uF IXYS 1kV U2 C12 Viso1 IXDD609SIA 2220 RG1 D 0.1uF CUI Inc 1 Q1 VCC 4.7 ± 5a 0805 VHS1-S12-S12-SIP 8 STMicroelectronics C1 VCC 1206 GND +12V 12 VDC @ 84mA Viso1 3 7 DRVGQ1 G STF5NK100Z 0.1uF EN OUT U8 1 7 DRVA 2 1000V +Vin +Vout 0805 IN S C37 C4 C5 C6 4 6 TO-220F Analog Devices Inc GND OUT 2.2 µ F 2.2 µ F 2.2 µ F 0.1uF 5 +5V ADUM1420BRWZ Viso1 GND TBH25P47R0JE Rsw1 0805 0805 0805 2 5 0805 Q1_SRC TAB Q1_SRC 8 2 -Vin -Vout GND 47R 25W GND Vdd1 VddA C53 C3 ISOLATION GND 8-SOIC DRIVE1 OUT1 DRVPOSB 9 1 DRVA 0.1uF TXa TXa 0805 0.1uF TBH25P47R0JE Rsw2 4 3 Q1_SRC DRV2 1kV NC4 GndA U5 47R 25W 5 IXYS 2220 NC5 R5 6 28 Viso3 IXDD509SIA NC6 VddB Viso2 RG2 D CUI Inc 1 Q2 100K GALVANIC VCC 4.7 ± 5a DRVNEGB 10 27 DRVB C38 VHS1-S12-S12-SIP 8 STMicroelectronics 100K C8 VCC 1206 TXb TXb 0.1uF +12V 12 VDC @ 84mA Viso3 3 7 DRVGQ2 G STF5NK100Z 0.1uF EN OUT 13 26 Q3_SRC 0805 1 7 DRVC 2 1000V GND Ed_Dis GndB +Vin +Vout 0805 IN S C39 C42 C43 4 6 TO-220F 25 GND OUT C32 NC25 22 2.2 µ F 0.1uF 2.2 µ F 5 VddC Viso3 GND GND1 0805 0805 2 5 0805 TAB HS1 ISOLATION C31 -Vin -Vout GND 0.1uF HS2 DRVNEGA 11 21 DRVC -HV1 1 2 Aavid Thermalloy 1 2 TXc TXc 0.1uF 1kV GND -HV1 8-SOIC 531002B00000G 0805 2220 24 20 NC24 GndC -HV1 19 23 NC19 GndC 18 17 Alternate: Micrel a MIC4422ZM NC18 VddD Viso4 GALVANIC C44 +HV2 DRVPOSA 12 16 DRVD C45 TXd TXd 0.1uF GND1 0805 7 15 0.1uF GND1 GndD -HV2 DRV3 14 1kV GND1 IXDD509SIA U3 2220 Viso2 IXYS GND 28-SOIC (7.5mm Width) RG3 D CUI Inc 1 Q3 VCC 4.7 ± 5a VHS1-S12-S12-SIP 8 STMicroelectronics C46 VCC 1206 +12V 12 VDC @ 84mA Viso2 3 7 DRVGQ3 G STF5NK100Z 0.1uF EN OUT 1 7 DRVB 2 1000V +Vin +Vout 0805 IN S C9 C10 C11 4 6 TO-220F GND OUT TBH25P47R0JE Rsw3 2.2 µ F 0.1uF 2.2 µ F 5 Q3_SRC GND 47R 25W 0805 0805 2 5 0805 Q3_SRC TAB -Vin -Vout GND C47 DRIVE2 OUT2 GND 8-SOIC TBH25P47R0JE Rsw4 0.1uF DRV4 +5V 47R 25W 1kV +5V IXYS U6 2220 GND GND Viso4 IXDD509SIA D R6 RG4 GND1 GND1 CUI Inc 1 Q4 4.7 ± 5a VCC 100K +12V +12V VHS1-S12-S12-SIP 8 STMicroelectronics C48 VCC 1206 100K +HV +HV +12V 12 VDC @ 84mA Viso4 3 7 DRVGQ4 G STF5NK100Z 0.1uF EN OUT -HV -HV 1 7 DRVD 2 1000V +Vin +Vout 0805 IN S C49 C54 C30 4 6 TO-220F DrvPosb GND OUT C55 DrvPosb 2.2 µ F 0.1uF 2.2 µ F 5 DrvPosa GND GND1 HS3 DrvPosa 0805 0805 2 5 0805 TAB HS4 DrvNegb -Vin -Vout GND 0.1uF Aavid Thermalloy 1 2 1 2 DrvNegb -HV2 DrvNega 1kV 531002B00000G DrvNega GND -HV2 8-SOIC 2220 TRIUMF Stores: 3-4/1319 BNC1 JMP1 +HV 3 2 +HV1 1 C26 GND1 R1 + Panasonic - ECG JMP2 470K 450V DC 10 µ F 3 PR02 2 +HV2 1 GND1 TRIUMF Stores: 3-4/1319 GND1 BNC2 JMP3 -HV 3 2 -HV1 C27 1 GND1 Panasonic - ECG R2 450V DC JMP4 470K 10 µ F 3 PR02 + 2 -HV2 1 GND1 GND1 Title Size Number Revision A3 Date: 16.05.2013 Sheet of File: D:\Copy of U\..\bradniels_3.SchDoc Drawn By: 1 2 3 4 5 6 7 8 42

BN gate trigger NIM signal, BN gate pulse 43

FPGA structure, schematics 44

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BN gate chopper setup without active focusing 47

Photo of the chopper setup The two BN gates are positioned in the CF100 cross pieces, the MCP is in the foreground 48

Protons passing the BN gates pulse slopes 500 eV proton TOF spectra. ± 300 V grid voltages. φ 1 mm Iris1, φ 5 mm Iris2, φ 1 mm Iris3 diameters. a. Source H 2 pressure 5 · 10 -4 mbar. Spike width 1.57 channels corresponding to dt = 3.83 ns and dT = 1.21 eV. b. Source H 2 pressure 5 · 10 -3 mbar. 1.09 channels wide, dt = 2.66 ns, dT = 0.92 eV. 49

Proton source line profile at p H2 = 5 · 10 -4 mbar 50

Proton source line profile at p H2 = 5 · 10 -3 mbar 51