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

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

Oct 27, 2022 433 likes •1.08k views

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. Gernhuser 1

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Towards a first measurement of the free neutron bound beta decay hydrogen atoms at a high flux beam reactor throughgoing beam tube

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  • E. Gutsmiedl1, W. Schott1, K. Bernert1, R. Engels2, T. Faestermann1, P. Fierlinger3, R.

Gernhäuser1,R. Hertenberger4, S. Huber1, I. Konorov1, B. Märkisch1, S. Paul1, C. Roick1, H. Saul1,

  • S. Spasova1, T. Udem5, A. Ulrich1

1Physik-Department, Technische Universität München, D-85748 Garching, Germany 2Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany 3Excellence Cluster Universe, Technische Universität München, D-85748 Garching, Germany 4Sektion Physik, Ludwig- Maximilian- Universität München, D-85748 Garching, Germany 5Max- Planck- Institut für Quantenphysik, D-85748 Garching, Germany

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Two- body neutron decay

n → H + 𝜉 TH = 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)

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Hyperfine spin states

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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)

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gS upper limit should be reduced by a factor 10 Hν should be measured within 10-3

  • 0.0026 < gT / gA < 0.0024 (C.L. 95 %)

(R. W. Pattie, Jr., et al. PRC 88, 048501 (2013)

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SLIDE 10

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Frm2 SR6 beam tube neutron and gamma flux

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Tn < 0.6 eV, Eγ < 0.5 MeV

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Ti-sapphire CO2

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E = (1 – R)-1 ≈ 106

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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

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PIK experimental setup

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H(2s) + Ar → H-+ Ar+ cross section

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σ (TH(2s) = 0.33 keV) ≈ 5 · 10-17 cm2

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Ar cell schematically

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Electrostatic quadrupole doublet

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Φ 3 cm aperture

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Pulsed electric deflector

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2 cm x 4 cm aperture

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Bradbury Nielsen gate chopper

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Expected H- rate

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ሶ NH = BR ( ׬ 𝜚 𝑨 Ω 𝑨 𝑒𝑊 )/ (4π τn vn ) = = BR 𝜄1

2 𝑠 𝑡 2 π zn ത

𝜚 / (2 τn vn ) = 7.3 s-1 with θ1 = 0.14 (8°), rs = 1.5 cm, zn = 0.5 m, ത 𝜚 = 1014 cm-2 s-1, ሶ NH(2s) = 0.73 s-1 p (lm = 0.176 m, σ = 5 · 10-21 m2 ) = 8.4 · 10-3 mbar P (H(2s) → H- ) = nAr σ Δz = 0.18, nAr = 2 · 1020 m-3 ሶ NH- = 0.13 s-1 P (H(2s) → H+ ) = 0.45 (2 laser) ሶ NH+ = 0.33 s-1

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N = 4.4 · 104 results ( ሶ NH+ = 0.33 s-1 ),

  • i. e., 1.5 d measuring time
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N = 8.3 · 105 results ( ሶ NH+ = 0.33 s-1 ),

  • i. e., 29 d measuring time
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Breit- Rabi diagram of the 2 S1/2 2 P1/2 hyperfine splitting

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W4

W4 obtained by measuring vββ = Nβ1-1 / Nβ00 vββ = N4 / (N1 sin2θ + N2 cos2θ) = = 2 N4 / (N1 + N2 - cos2θ (N1 - N2 )) for B << Bc , 2θ ≈ π/2, cos2θ ≈ 0 vββ = 2 N4 / (N1 + N2 ) → W4 ≈ (1/2) vββ for B large, cos2θ ≈ 1 vββ = N4 / N2

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being 7.9 % of W3 (≈ dW3 ) background eliminated by ionizing these (n>2)s H atoms using a λ = 1.458 µm laser

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Mockup setup

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W.Schott et al., MLL Annual Report 2014,

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Cup H- current vs. spin filter magnet current

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Cup current vs. counter field grid voltage

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D

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Differentiated

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Difference between 𝑈𝐼− and TH

H(2s): 𝑈𝐼− = TH + 10.2 eV = = 335.9 eV dTH = E0 β dv/c = 5.7 eV Δt / t = - (1/2) ΔTH / TH , t = 4 µs at s = 1m, Δt = 63 ns

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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

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SLIDE 39

BN Gate

How the BN gates functions:

  • HVTyp = 250 V /grid (HVmax = 500V)
  • use two grids intercalated in one plane
  • HV1 = +250 V
  • HV2 = -250 V

Gate open Gate closed Example: charged particles

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BN gate photo- etched grid

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Newcut 434 East Union St. Newark, NY 14513, USA

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Grid dimensions (mil)

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α = π q Uwire/ (2TH- ln (1/ tan(π / (4a/r)))) = 22.3°, Uwire = ± 200 V, 2a = 43.5 mil, 2r = 5 mil

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Pulse generation for BN gate grids

1 2 3 4 5 6 7 8 Title Number Revision Size A3 Date: 16.05.2013 Sheet of File: D:\Copy of U\..\bradniels_3.SchDoc Drawn By: 4.7 ±5a 1206 RG1 Viso1 4.7 ±5a 1206 RG2 2.2µF 0805 C6 4.7 ±5a 1206 RG3 G D S TO-220F STMicroelectronics STF5NK100Z 1000V Q3 4.7 ±5a 1206 RG4 0.1uF 2220 1kV C45 0.1uF 2220 1kV C55 G D S TO-220F STMicroelectronics STF5NK100Z 1000V Q4 G D S TO-220F STMicroelectronics STF5NK100Z 1000V Q2 G D S TO-220F STMicroelectronics STF5NK100Z 1000V Q1 GND +12V 2.2µF 0805 C4 0.1uF 0805 C5 Viso2 2.2µF 0805 C11 GND +12V 2.2µF 0805 C9 0.1uF 0805 C10 Viso3 2.2µF 0805 C43 GND +12V 2.2µF 0805 C39 0.1uF 0805 C42 DRVD DRVGQ1 Viso1 DRVA Viso3 DRVGQ2
  • HV1
DRVC Viso4
  • HV2
DRVB DRVGQ3 DRVGQ4 0.1uF 2220 1kV C3 0.1uF 2220 1kV C47 0.1uF 0805 C1 OUT1 OUT2 +HV1 +HV2
  • HV1
  • HV2
CUI Inc VHS1-S12-S12-SIP 12 VDC @ 84mA +Vin 1
  • Vin
2
  • Vout
5 +Vout 7

U2

CUI Inc VHS1-S12-S12-SIP 12 VDC @ 84mA +Vin 1
  • Vin
2
  • Vout
5 +Vout 7

U3

CUI Inc VHS1-S12-S12-SIP 12 VDC @ 84mA +Vin 1
  • Vin
2
  • Vout
5 +Vout 7

U5

1 2 531002B00000G Aavid Thermalloy HS1 1 2 531002B00000G Aavid Thermalloy HS3 0.1uF 0805 C8 0.1uF 0805 C46 0.1uF 0805 C48 DRIVE2 DRIVE1 IXYS IXDD609SIA 8-SOIC IN 2 OUT 6 GND 4 VCC 1 GND TAB VCC 8 OUT 7 EN 3 GND 5 DRV1 Viso4 2.2µF 0805 C30 GND +12V 2.2µF 0805 C49 0.1uF 0805 C54 CUI Inc VHS1-S12-S12-SIP 12 VDC @ 84mA +Vin 1
  • Vin
2
  • Vout
5 +Vout 7

U6

Viso2 IXYS IXDD509SIA 8-SOIC IN 2 OUT 6 GND 4 VCC 1 GND TAB VCC 8 OUT 7 EN 3 GND 5 DRV2 IXYS IXDD509SIA 8-SOIC IN 2 OUT 6 GND 4 VCC 1 GND TAB VCC 8 OUT 7 EN 3 GND 5 DRV3 IXYS IXDD509SIA 8-SOIC IN 2 OUT 6 GND 4 VCC 1 GND TAB VCC 8 OUT 7 EN 3 GND 5 DRV4 GND1 GND1 0.1uF 2220 1kV C7 GND1 0.1uF 2220 1kV C32 GND1 1 2 HS2 1 2 HS4 Alternate: Micrel a MIC4422ZM Q3_SRC Q1_SRC Q1_SRC Q3_SRC TRIUMF Stores: 3-4/1319 BNC1 TRIUMF Stores: 3-4/1319 BNC2 Viso1 0.1uF 0805 C53 0.1uF 0805 C44 Viso2 DRVA DRVB GND +5V 2.2µF 0805 C37 GND 28-SOIC (7.5mm Width) Analog Devices Inc ADUM1420BRWZ 9 VddA 2 GndB 26 GALVANIC ISOLATION Vdd1 8 TXa TXa GND1 7 GndA 3 1 10 TXb TXb 27 NC25 25 NC24 24 Ed_Dis 13 NC19 19 NC18 18 VddB 28 GndC 20 11 TXc TXc 21 VddC 22 GndD 15 12 TXd TXd 16 VddD 17 ISOLATION GALVANIC NC4 4 NC5 5 NC6 6 GND1 14 GndC 23

U8

0.1uF 0805 C38 Viso3 DRVC DRVD
  • HV2
GND 0.1uF 0805 C12 GND Viso4 0.1uF 0805 C31
  • HV1
Q1_SRC Q3_SRC 100K R5 100K 100K R6 100K GND1 GND1
  • HV
+HV1
  • HV1
+HV2
  • HV2
+HV 470K PR02 R1 470K PR02 R2 + Panasonic - ECG 450V DC 10µF C27 + Panasonic - ECG 450V DC 10µF C26 1 2 3 JMP1 GND1 1 2 3 JMP2 GND1 1 2 3 JMP3 1 2 3 JMP4 GND1 GND1 GND GND1 +12V +HV
  • HV
DrvPosa DrvNega GND +12V GND1 +HV
  • HV
TBH25P47R0JE 47R 25W Rsw1 TBH25P47R0JE 47R 25W Rsw2 TBH25P47R0JE 47R 25W Rsw3 TBH25P47R0JE 47R 25W Rsw4 +5V +5V DrvNega DrvNegb DrvPosb DrvPosa DrvPosb DrvNegb DRVPOSB DRVNEGB DRVNEGA DRVPOSA

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HV pulse generation DC/DC converter FET driver FPGA signals

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BN gate trigger NIM signal, BN gate pulse

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FPGA structure, schematics

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BN gate chopper setup without active focusing

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Photo of the chopper setup

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The two BN gates are positioned in the CF100 cross pieces, the MCP is in the foreground

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Protons passing the BN gates pulse slopes

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500 eV proton TOF spectra. ± 300 V grid voltages. φ1 mm Iris1, φ5 mm Iris2, φ1 mm Iris3

  • diameters. a. Source H2 pressure 5 · 10-4 mbar. Spike width 1.57 channels corresponding to dt =

3.83 ns and dT = 1.21 eV. b. Source H2 pressure 5 · 10-3 mbar. 1.09 channels wide, dt = 2.66 ns, dT = 0.92 eV.

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Proton source line profile at pH2 = 5 · 10-4 mbar

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Proton source line profile at pH2 = 5 · 10-3 mbar

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500 eV p TOF spectrum at pH2 = 4 · 10-4 mbar

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± 300 V BN gate chopper grid voltages. φ1 mm Iris1, φ5 mm Iris2, φ5 mm Iris3 diameters

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Secondary electron yield measurement

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BN gate chopper setup modified by a degrader. Protons of keV energy pass thin foils of carbon, silver and plastics coated with MgO or LiF. The produced keV secondary electrons are measured by an MCP.

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TOF spectra at pH2 = 3 · 10-3 mbar

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± 300 V BN gate chopper grid voltages. φ5 mm Iris1, Iris2, Iris3

  • diameters. Blue. 18 keV sec. electrons, produced by 18.5 keV protons,

having hit a 17 µg/cm2 C foil coated with 10 Å LiF. Red. Open zero voltage foil frame 500 eV protons. 3.1 electron/ incident p.

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Electrostatic focusing using a quadrupole doublet

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  • Electrostat. quadrupole doublet, schematically

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Q1, Q2: L=1cm, aperture radius r=1.5cm, l=3cm, Q1: 1/f1 ≈ 𝑙1

2L;

k1 = r-1 √(Φ1/Us), Q2: f2 , k2 , Φ2 , for f1 = f2 = f, Φ1 = Φ2 = Φ, doublet focal length f*

, ,

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Quadrupole doublet focused 500 eV p TOF spectrum

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pH2 = 7 · 10-3 mbar. ± 300 V BN gate chopper grid

  • voltages. φ5 mm Iris1, Iris2, Iris3 diameters.
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Q doublet focusing onto an electric deflector

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Electric deflector, schematically

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Two electrodes radii R1 and R2, reference particle radial coordinate r. Double- focusing with focal points in horizontal (x- y) and vertical planes being at the same position. E(r)=UR1 R2 /(r2 (R2 – R1)) = 2T/(qr), T=500 eV, r=5 cm, R1 = 4 cm, R2 = 6 cm, U=416.8 V

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Deflector dispersion

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Deflected intensity vs. Q doublet voltage Φ

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T=500 eV, U/2 = ± 220 V

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Outlook

Functioning: BN gate chopper with electrostatic Q doublet focusing and electric deflector H(2s) detection by charge exchanging in Ar cell

Measurements: BOB H(1s) and H(2s) atoms (Ar cell,

focusing element, deflector, BN gate chopper, MCP) BOB H(2s) hyperfine state population probability (spin filter, Ar cell etc.) Nα11/ Nα10 → χ (gS, gT ) Nβ1-1/ Nβ00 , Nβ1-1/ Nα10 , Nβ1-1/ Nα11 → W4 (Hν )

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