Bertram Blank CEN Bordeaux-Gradignan main physics goals detector scans source measurements MC simulations ISOLDE workshop, December 5-7, 2011

Determination of experimental values for 0 +  0 + :  measurement of T 1/2, BR, Q EC  vector coupling constant G v (CVC hypothesis)  V ud element of CKM quark matrix Precision required: < Future subjects: - experimental tests of isospin corrections  c - test of CVC on larger range - measurements with more exotic isotopes  Measurements for A > 54  Measurements for Tz ≤ -1 Ft =  0.75 s Ft = ft (1 +  ’ R ) (1 +  NS -  C ) = for T=1 K 2 G 2 v (1+  v R )

beam preparation with REXtrap Half-life of 38 Ca: B. Blank et al., EPJA 44 (2010) 363 BR = 75.45(58)% ISOLDE 2007 T 1/2 = ± 1.9 ms Kavanagh et al. Zioni et al. Present work Gallman et al. Wilson et al.

basically 100% super-allowed decay very small non-analog decays precision of e.g. 10% for a 1% transition:  0.1%

many decay channels open strong non-analog transitions high precision of  efficiency needed  0.1%

thick dead zone on interior side thin external dead layer request of high-precision for crystal size crystal position dead zones large dewar aluminum entrance window

X-ray radiography  -ray detector scans source measurements MC simulations (GEANT4 or CYLTRAN)  develop a model of the detector to calculate efficiency at any energy at a fixed distance of 15 cm

 rough size of crystal  tilt of crystal with respect to detector housing of 1°  according to GEANT4 simulations no influence on results

AGATA scan table at CSNSM: strongly collaminated 137 Cs source HPGe X-Y table 137 Cs (477MBq) A. Korichi et al.

AGATA scan table at CSNSM: strongly collaminated 137 Cs source (662 keV) HPGe X-Y table 137 Cs (477MBq)

Scan at CENBG: strongly collaminated 241 Am source (60 keV)

total full-energy peak excellent full-energy peak spectrum good total-energy spectrum problem with thickness of entrance window?

total full-energy peak tilt…. full-energy peak: excellent total spectrum: raisonable precision of the stepping motors: 10 -2

Source position high-precision X-Y-Z table all source measurements at exactly 15 cm from entrance window   position precision of better than 0.1%

Fixed 137 Cs and movable 241 Am: 6  s of shaping time

To develop detector model: which code to use: GEANT4, CYLTRAN, EGGS…. GEANT4: (J. Souin, PhD student…. he quit….) almost all features needed errors in decay schemes  external event generator no  -  correlations (1% effect)  external event generator not extremely well tested for low-energy  rays different packages, which one to use? CYLTRAN: (BB) very well tested  J. Hardy FORTRAN77… only single  rays or electrons in the input  upgrade to « source-type » input via an external event generator positron annihilation-in-flight not included  to be included; significant effect on escape peaks which code to use: GEANT4, CYLTRAN, EGGS….

two ways: correct experimental data for summing effects to get single  -ray efficiencies certain number of approximations « collimated » simulations, opening cone:  much less events to simulate peak-to-total can be included a posteriori  J. Hardy et al. to simulate whole decay schemes no approximations needed as long as decay scheme is known need of event generator including  angular correlations peak-to-total needed in simulations need of a lot of simulated events to get statistics for all  rays!!  B. Blank et al. presently only CYLTRAN simulations

peak-to-total sources:  one single  ray with 100% branching ratio 57 Co, 51 Cr, 85 Sr, 137 Cs, 58 Co, 54 Mn, 60 Co, 22 Na 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, 152 Eu, 207 Bi short-lived online source at ISOLDE: 24 Na, 27 Mg, 56 Co, 66 Ga, 75 Se one absolute efficiency source: 60 Co with activity precision of 0.7‰

57 Co 51 Cr 85 Sr 54 Mn 60 Co

+ 133 Ba, 56 Co

vendor specifications adjusted parameters length of crystal79.2 mm79.25 mm radius of crystal34.8 mm34.54 mm length of central hole59.5 mm71.2 mm radius of central hole5 mm7.15 mm external dead zone <0.5  m0.5  m internal dead zone0.5 mm end dead zone0.5 mm1 mm distance window - crystal5 mm5.73 mm !!!!

rescan front with 241 Am check entrance window thickness measure entrance window to cristal distance test pile-up correction for different energies and shaping times improve sources 133 Ba and 56 Co add sources 66 Ga, 75 Se, 134 Cs, 152 Eu measure other sources: peak-to-total: 139 Ce, 7 Be, 65 Zn, 28 Al, 37 S efficiency: 46 Sc, 59 Fe, 108m Ag, 120 Sb, 180m Hf, 66 Ga add annihilation in flight to CYLTRAN compare with GEANT4 simulations analyse for single  -ray efficiency  detector model with % efficiency precision

J. Souin, PhD student A. Korichi and Hoa Ha, CSNSM A. Herlert and K. Johnston, ISOLDE J. Hardy, Texas A & M Exotic Nuclei group at CENBG Born to be wild….. Thanks for your attention! … or what????

full-energy peak nice over-all agreement holding structure reasonably well reproduced

full-energy peak slight difference… there was a problem during the scan…

total full-energy peak good agreement for full-energy peak reasonable agreement for total spectrum

full-energy peak does not help a lot… effect of holding structure very important

 detector Ge detectors Tape transport system Q EC T 1/ BR  38 Ca ISOLDE beam from REXtrap

fixed 137 Cs source and pulser on other channel

137 Cs: conversion electrons 57 Co 51 Cr 85 Sr 137 Cs 54 Mn 60 Co