Bertram Blank CEN BordeauxGradignan Germanium detector calibration experimental
Bertram Blank CEN Bordeaux-Gradignan • Germanium detector calibration • experimental studies: 0+ - 0+ b decay mirror b decay • future work ISOLDE workshop and users meeting, December 2 -4, 2015
• • • What can we learn? ( * )
• • • Nuclear beta decay 0+ → 0+ : T 1/2 QEC Ft = ft (1 + d. R’ ) (1 – dc + d. NS ) = f(Z, QEC) ~ 1. 5% K g. V 2 (1 + DR) M F f(weak interaction) ~ 2. 4% 0+ 1/2+ T 1/2 additional measurement needed K mirror decays: Ft = ft (1 + d. R’ ) (1 – dc + d. NS ) = g. V 2 (1 + DR) M F 1 (1 + fa/fv) r 2 QEC 1/2+ = cnst f(nucl. structure) ~ 0. 3 -1. 5% BR BR 2 2 x = cnst Precision measurements required: 10 -3 ü QEC → mass measurements: f ~ QEC 5 ü T 1/2, BR → b-decay studies: t = T 1/2 / BR → b-decay angular correlation studies ü r 2
Germanium detector calibration
• close to 100% g. s. to g. s. transition • low precision needed for non-analog transitions
• many decay channels open • strong non-analog transitions • high precision of g efficiency needed 0. 1%
B. Blank et al. , NIMA 776 (2015) 34 • • • Calibration of germanium detector • Derel = 0. 1%, Deabs = 0. 15% • calibration programme of a HP Ge detector: - x-ray photography of detector - scan of the crystal at CSNSM - source measurements - MC simulations: CYLTRAN, GEANT 4 De < 5 ‰ De < 1. 5 ‰ X-ray photography Scan at CSNSM Branching ratios: 24 Na, 27 Mg, 48 Cr, 56 Co, 60 Co, 66 Ga, 75 Se, 88 Y, 133 Ba, 134 Cs, 137 Ce, 152 Eu, 180 Hf, 207 Bi Peak/total: 22 Na, 41 Ar, 51 Cr, 54 Mn, 57 Co, 58 Co, 65 Zn, 85 Sr …ISOLDE sources
0+ - 0+ b decay: 38 Ca
• many decay channels open • strong non-analog transitions • high precision of g efficiency needed 0. 1%
• • • 38 Ca production at GANIL/LISE 3 Primary Beam: 40 Ca @ 50 Me. V/A Production Target : nat. Ni 90 mm LISE 3 Spectrometer • 104 38 Ca / s • 99. 5 % purity • Contaminants: • 37 K: 0. 12 % • 36 Ar: 0. 11 % • 35 Cl: 0. 09 % • 34 S: 0. 14 % Detection Set-up
• • • 38 Ca branching ratios and half-life Present work and A
• • • 38 Ca: result • half-life: 443. 70(25) ms • BR (0+ — 0+): present: Park et al. : 77. 25(15) % 77. 09(35) % 77. 28(16) % • Q value: 6612. 11(7) ke. V Eronen et al. : è ft = 3063. 3(62) s è Ft = 3077. 5(67) s
• • • 38 Ca: result …. 14 nuclei BR for all Tz = -1 nuclei largest error
Recent ISOLDE experiment: 10 C
• • • 0+ decays: limits on exotic currents • assumption: only vector current Severijns et al. • limit on scalar currents: b. F = Re( (Cs + C’s) / Cv ) = 0. 0026(42) (90% CL) • limit on scalar current from b decay: |Cs / Cv | 0. 065 improve on low-Z nuclei Hardy & Towner
• • • 0+ decays: 10 C error budget • BR by far largest error • two precise measurements • Savard et al. : 1. 4625(25)% (PRL 74 (1995) 1521) • Fujikawa et al. : 1. 4665(38)% (PLB 449 (1999) 6) èmeasurements with Ge multi-detector array our approach: high-precision single-crystal germanium detector
• • • 10 C decay scheme measurement of relative branching ratio
• • • Experimental setup • many proton pulses • nano. Ca. O + VD 7 • HRS to LA 1 10 CO u s” u o o n nti “c g 15 cm am e b
• • • First steps of analysis • 1022 ke. V line from 19 Ne (same T 1/2, same QEC): no 1022 ke. V peak, only 511 -511 pile-up
• • • First steps of analysis • 1022 ke. V line from 10 C: Ø 1022 ke. V line + 511+511 pile-up
• • • First steps of analysis • 1022 ke. V line from 10 C: Ø 1022 ke. V line + 511+511 pile-up
• • • First steps of analysis 1022 ke. V line from 10 C: different ways to analyse Ø Fitting with a fixed shape for pile-up peak determined from 19 Ne Ø Calculate the number of pile-ups from 511 ke. V singles peak Ø Measurements with different shaping times different pile-up probabilities Ø Measurements at different distances different pile-up probabilities Ø Other problem: at A=26 (CO) a lot of 13 N 2
Mirror b decay: 23 Mg and 27 Si
• • • Experiment JYFL 2013: 23 Mg & 27 Si 24 / 25
• • • BR of 23 Mg preliminary è 92. 05(8) % C. Magron et al. Literature value: (91. 78± 0. 26)%
• • • Half-life of 23 Mg preliminary T 1/2 (s) preliminary C. Magron et al. runs
• • • Half-life of 23 Mg T 1/2 (s) preliminary Az 75 C. Magron et al. Go 68 Az 77 Al 74 Az 74 Preliminary Résultat préliminaire result
• • • Half-life of 27 Si T 1/2 (s) preliminary C. Magron et al. Mi 58 Gr 71 Su 62 Az 75 Bl 68 Ge 76 Go 68 Ba 77 Résultat Preliminary préliminaire result
• • • Uncertainties for 23 Mg and 27 Si preliminary need to measure GT/F mixing C. Magron et al. old values
Future plans at ISOLDE
• • • Half-lives of 10 C and 18 Ne ISOLDE rates: 6. 9 E+05
• • • Branching ratio of 22 Mg è Extent high-precision efficiency calibration below 100 ke. V ISOLDE rates: 8. 0 E+06 pps
• • • Conclusions • High-precision Germanium detector is available Tz = -1 nuclei can be addressed: 18 Ne, 22 Mg, 26 Si, 30 S, 42 Ti • Big potential for nuclear mirror decays need for high-precision GT-F mixing ratio measurements • What about Tz = -2 nuclei? 32 Ar, 36 Ca… • SPIRAL 2/S 3/DESIR: heaviest N=Z odd-odd nuclei èCVC tests over much broader range • b-n correlation measurements in a supra-conducting magnet • Improve theoretical corrections….
Collaborations: CENBG, IGISOL, GANIL, IPNO, IPHC, TRIUMF
Source position high-precision X-Y-Z table • all source measurements at exactly 15 cm from entrance window position precision of better than 10 mm
• X-ray radiography • g-ray detector scans • source measurements • MC simulations (GEANT 4 or CYLTRAN) è develop a model of the detector to calculate efficiencies at any energy at a fixed distance of 15 cm
è rough size of crystal è tilt of crystal with respect to detector housing of 1° è according to GEANT 4 simulations no influence on results
• AGATA scan table at CSNSM: strongly collaminated 137 Cs source HPGe X-Y table 137 Cs (477 MBq) A. Korichi et al.
• excellent full-energy peak spectrum • good total-energy spectrum
total full energy • effect of detector tilt clearly visible • reasonable overall agreement
total full energy • effect of detector tilt clearly visible • reasonable overall agreement
• peak-to-total sources: close to « one single g ray with 100% branching ratio » • standard sources: 57 Co, 51 Cr, 85 Sr, 137 Cs, 54 Mn, 60 Co, 22 Na • short-lived online sources at ISOLDE: 58 Co, 65 Zn, 41 Ar • relative efficiency sources: a few well-known branches (BR error <1%) at largely different energies • standard sources: 60 Co, 88 Y, 133 Ba, 134 Cs, 137 Cs, 152 Eu, 207 Bi • short-lived online sources at ISOLDE and IPN Orsay: 24 Na, 27 Mg, 48 Cr, 56 Co, 66 Ga, 75 Se, 180 m. Hf • absolute efficiency: • 60 Co with activity precision of 0. 7‰ • g-g coincidences
Calibration of germanium detector: peak-to-total T/P (exp) sim: no backscatter material sim: with backscatter material
• • • Calibration of germanium detector: absolute efficiency relative measurement: all sources absolute measurement: 60 Co
De < 5 ‰ • • • Calibration of germanium detector: absolute efficiency De < 1. 5 ‰ 60 Co Fit 1: Fit 2: P 0 = -0. 016 ± 0. 061; 2 = 0. 85 < 0. 6 ‰ precision P 0 = -0. 09 ± 0. 48 P 1 = 0. 02 ± 0. 16; 2 = 0. 86
• • • Absolute efficiency calibration with g-g coincidences Condition: • g-g cascade with large BR • no « cross-over » transition 60 Co (et 24 Na) source X Ge 4+ 2+ Eg 1, Br 1 = 99. 85 % I 1 0+ Eg 2, BR 2 = 99. 99826 % I 2 X Eg 1 + Eg 2 , BR 12 I 12 • standard pile-up is same for all peaks • but: necessity to correct pile-up between two events (11731 + 13322 et vice-versa) • I 1 = A 0 * e 1 * BR 1 * (1. -et 2 * w 12( )) • I 2 = A 0 * e 2 * BR 2 * (1. -et 1 * w 12( )) • I 12 = A 0 * e 1 * e 2 * BR 12 * w 12( ) • I 12 = I 12’ – I 12_11 – I 12_22 • I 12_11 = I 11 * e 2 / e 1 * BR 2 / BR 1 • I 12_22 = I 22 * e 1 / e 2 * BR 1 / BR 2 • et 2 : from other measurements • w 12( ): from calculations • three unknowns: A 0, e 1, e 2 • three equations e 1, e 2
• • • Absolute efficiency with g-g coincidences: 1173+1332 60 Co 1173+1332 1173 + 1173 1332 + 1332 è e 1 (g-g) = (0. 2186 ± 0. 0007) % e 1 (source act. ) = (0. 2175 ± 0. 0003) % è e 2 (g-g) = (0. 1996 ± 0. 0007) % e 2 (source act. ) = (0. 1996 ± 0. 0003) % … do 24 Na at ISOLDE?
• • • 38 Ca detection
0+ 0+ decays: status • 14 nuclei measured with precision of order 10 • Vud = 0. 97417 ± 0. 00021, S Vux = 0. 99978 ± 0. 00
• • • Half-lives of 27 Si preliminary C. Magron et al.
Future plans: GANIL – SPIRAL 2 – S 3 – DESIR • Tz = -1, 0+ - 0+ decays • heavy 0+ - 0+ decays
• • • Super-allowed emitter production at GANIL/LISE 3 Primary Beam: 28 Si, 32 S, 46 Ti @ 50 Me. V/A Production Target : nat. Ni 90 mm LISE 3 Spectrometer • 26 Si • 30 S • 42 Ti • … Detection Set-up
• • • SPIRAL 2 facility Phase 1+ Phase 2 • NFS and S 3 experiments • for DESIR: • SPIRAL 1 (light nuclei from beam/target fragmentation) • SPIRAL 2 (n-rich fission fragments, transfer and fusion-evaporation products) at earliest 2020 • S 3 (fusion-evaporation, refractory elements)
• • • Heavy Tz = 0 nuclei isotope half-life (ms) 66 As 95. 77(23) 79. 1(8) production rate (pps) 50000 35000 64. 776(30) 54(5) 50(5) 55(6) 15(7) 37(18) 37(5) 30000 1500 300 250 200 400 0. 3 70 Br 74 Rb Tz = 0 78 Y 82 Nb 86 Tc 90 Rh 94 Ag 98 In test CVC over a larger range of Z
• • • Heavy Tz = 0 nuclei
• • • PIPERADE at DESIR Double Penning trap for high-resolution Requirements • Purify large samples (>104 ions) separation at DESIR facility of SPIRAL 2 • Mass resolution > 105 Test set-up at • Fast separation methods CENBG Bordeaux P. Ascher et al. , EPJ Web of Conf. 66, 11002 (2014) Collaboration: • CEN Bordeaux-Gradignan • MPIK Heidelberg • CSNSM Orsay • GANIL Caen • LPC Caen
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