The Next Generation Beam Neutron Lifetime Experiment F . E. - PowerPoint PPT Presentation

The Next Generation Beam Neutron Lifetime Experiment F . E. Wietfeldt Tulane University

Our Plan Based on Sussex-ILL-NIST beam neutron lifetime program using quasi-Penning proton trap. More than 30 years experience with this program; many systematics thoroughly studied and understood.

Our Plan Based on Sussex-ILL-NIST beam neutron lifetime program using quasi-Penning proton trap. More than 30 years experience with this program; many systematics thoroughly studied and understood. Goal #1: Further explore, cross check, and reduce all systematic uncertainties to the 10 level -4

Our Plan Based on Sussex-ILL-NIST beam neutron lifetime program using quasi-Penning proton trap. More than 30 years experience with this program; many systematics thoroughly studied and understood. Goal #1: Further explore, cross check, and reduce all systematic uncertainties to the 10 level -4 Goal #2: Reduce the neutron lifetime uncertainty, using the beam method, to < 0.2 s

Brief Review of the 2005 NIST Beam Neutron Lifetime Experiment and 2013 Update

Brief Review of the 2005 NIST Beam Neutron Lifetime Experiment and 2013 Update Z φ ( v ) A beam L det proton counting rate: R p = ε p v dv τ n Z φ ( v ) neutron counting rate: R n = ε th A beam v th v dv

Brief Review of the 2005 NIST Beam Neutron Lifetime Experiment and 2013 Update Z φ ( v ) A beam L det proton counting rate: R p = ε p v dv τ n = R n ε p L det τ n R p ε th v th Z φ ( v ) neutron counting rate: R n = ε th A beam v th v dv

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V)

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det R p ε th v th

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det L det = nl + L end R p ε th v th

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det L det = nl + L end R p ε th v th # trap electrodes

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det L det = nl + L end R p ε th v th # trap electrodes length of � electrode + spacer

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det L det = nl + L end R p ε th v th total effective � # trap electrodes end region length length of � electrode + spacer

alpha, triton detector precision proton B = 4.6 T aperture detector neutron beam 6 Li mirror trap electrodes door closed deposit (+800 V) (+800 V) τ = R n ε p L det L det = nl + L end R p ε th v th total effective � # trap electrodes end region length length of � electrode + spacer ε p ⎛ ⎞ R p ( ) = τ − 1 ⎟ nl + L end ⎜ ε th v th ⎝ ⎠ R n

Proton Trap

1000 Prot oton on Pulse Height Sp Spectrum 2 Au) (32.5 ( .5 kV; 2 kV; 20 µ µg/cm /cm Au) 100 Counts 10 32.5 keV 1 0 100 200 300 400 500 600 ADC Channel (7.47 ch. = 1 keV)

Proton Arrival Time Spectrum 1000 2 Au) (32.5 kV; 20 µg/cm 3 Electrodes 4 Electrodes 100 5 Electrodes Counts 6 Electrodes 7 Electrodes 8 Electrodes 9 Electrodes 10 Electrodes 10 1 0 100 200 300 400 500 TDC Channel (6.25 ch/µs)

-3 4.0x10 Nor orma malized Prot oton on Cou ounts vs. Trap Length 2 Au) ( (32.5 .5 kV; 2 kV; 20 µ µg/cm /cm Au) 3.5 Proton-Bkdg/Alpha 3.0 2.5 2.0 1.5 2 3 4 5 6 7 8 9 10 11 Electrode Number Fit of R p 40 vs . number 20 R n Residuals 0 trap electrodes -20 -6 -40x10 2 3 4 5 6 7 8 9 10 11 Electrode Number 40 20 Residuals 0 -20 -6 -40x10 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 9/29/00 9/30/00 10/1/00 10/2/00 10/3/00 Date/Time

Lifetime vs. Backscatter 910 905 extrapolated result 886.8 ± 1.2 s measured lifetime (s) 900 (stat. error only) 895 27.5 kV 890 30 kV 32.5 kV 885 880 -3 0 5 10 15 20 25 30x10 backscatter fraction

1/v neutron counter

1/v neutron counter neutron detection efficiency: ε th = σ th ( ) ( ) θ x , y ( ) dxdy ∫ ∫ Ω x , y ρ x , y 4 π

1/v neutron counter neutron detection efficiency: ε th = σ th ( ) ( ) θ x , y ( ) dxdy ∫ ∫ Ω x , y ρ x , y 4 π Si detector solid angle

1/v neutron counter neutron detection efficiency: ε th = σ th ( ) ( ) θ x , y ( ) dxdy ∫ ∫ Ω x , y ρ x , y 4 π Si detector solid angle areal density of Li foil

1/v neutron counter neutron detection efficiency: ε th = σ th ( ) ( ) θ x , y ( ) dxdy ∫ ∫ Ω x , y ρ x , y 4 π Si detector solid angle neutron beam density areal density of Li foil

J. S. NICO et al. PHYSICAL REVIEW C 71 , 055502 (2005) Error Budget Source of correction Correction (s) Uncertainty (s) 6 LiF deposit areal density 2.2 6 Li cross section 1.2 Neutron detector solid angle 1.0 Absorption of neutrons by 6 Li + 5.2 0.8 Neutron beam profile and detector solid angle + 1.3 0.1 Neutron beam profile and 6 Li deposit shape − 1.7 0.1 Neutron beam halo − 1.0 1.0 Absorption of neutrons by Si substrate + 1.2 0.1 Scattering of neutrons by Si substrate − 0.2 0.5 Trap nonlinearity − 5.3 0.8 Proton backscatter calculation 0.4 Neutron counting dead time + 0.1 0.1 Proton counting statistics 1.2 Neutron counting statistics 0.1 Total − 0.4 3.4 2005: τ = 886.3 ± 3.4 s n

J. S. NICO et al. PHYSICAL REVIEW C 71 , 055502 (2005) Error Budget Source of correction Correction (s) Uncertainty (s) can be significantly 6 LiF deposit areal density 2.2 reduced by an 6 Li cross section 1.2 absolute calibration Neutron detector solid angle 1.0 of the Absorption of neutrons by 6 Li + 5.2 0.8 1/v neutron counter Neutron beam profile and detector solid angle + 1.3 0.1 Neutron beam profile and 6 Li deposit shape − 1.7 0.1 Neutron beam halo − 1.0 1.0 Absorption of neutrons by Si substrate + 1.2 0.1 Scattering of neutrons by Si substrate − 0.2 0.5 Trap nonlinearity − 5.3 0.8 Proton backscatter calculation 0.4 Neutron counting dead time + 0.1 0.1 Proton counting statistics 1.2 Neutron counting statistics 0.1 Total − 0.4 3.4 2005: τ = 886.3 ± 3.4 s n

Absolute neutron flux measurement to < 0.1% precision The Alpha-Gamma device HPGe detector • 10 B alpha-gamma device Totally absorbing 10 B target foil Neutron fluence monitor now working at NIST Monochromatic neutron beam 0.06% precision recently achieved! (Andrew Yue, NIST) PIPS detector with aperture HPGe detector Alpha-Gamma device • 3 He gas scintillation chamber (Tulane, NIST) - in construction/testing • neutron radiometer (Indiana, Michigan) - under development

Absolute neutron flux measurement to < 0.1% precision The Alpha-Gamma device HPGe detector • 10 B alpha-gamma device Totally absorbing 10 B target foil Neutron fluence monitor now working at NIST Monochromatic neutron beam 0.06% precision recently achieved! (Andrew Yue, NIST) PIPS detector with aperture 2013 improved result: HPGe detector Alpha-Gamma device τ = 887 .7 ± 2.3 s n • 3 He gas scintillation chamber (Tulane, NIST) - in construction/testing • neutron radiometer (Indiana, Michigan) - under development

900 neutron lifetime results since 1990 895 890 neutron lifetime (s) τ n = 888.0 ± 2.1 s 885 880 τ n = 879.6 ± 0.6 s 875 beam method UCN bottle 870 1990 1995 2000 2005 2010 2015 year

BEAM NEUTRON LIFETIME THE NEXT GENERATION

2005 Error Budget Source of correction Correction (s) Uncertainty (s) 6 LiF deposit areal density 2.2 6 Li cross section 1.2 Neutron detector solid angle 1.0 Absorption of neutrons by 6 Li + 5.2 0.8 Neutron beam profile and detector solid angle + 1.3 0.1 Neutron beam profile and 6 Li deposit shape − 1.7 0.1 Neutron beam halo − 1.0 1.0 Absorption of neutrons by Si substrate + 1.2 0.1 Scattering of neutrons by Si substrate − 0.2 0.5 Trap nonlinearity − 5.3 0.8 Proton backscatter calculation 0.4 Neutron counting dead time + 0.1 0.1 Proton counting statistics 1.2 Neutron counting statistics 0.1 Total − 0.4 3.4

2005 Error Budget Source of correction Correction (s) Uncertainty (s) 6 LiF deposit areal density 2.2 6 Li cross section 1.2 neutron Neutron detector solid angle 1.0 counting Absorption of neutrons by 6 Li + 5.2 0.8 Neutron beam profile and detector solid angle + 1.3 0.1 Neutron beam profile and 6 Li deposit shape − 1.7 0.1 Neutron beam halo − 1.0 1.0 Absorption of neutrons by Si substrate + 1.2 0.1 Scattering of neutrons by Si substrate − 0.2 0.5 Trap nonlinearity − 5.3 0.8 Proton backscatter calculation 0.4 Neutron counting dead time + 0.1 0.1 Proton counting statistics 1.2 Neutron counting statistics 0.1 Total − 0.4 3.4