coulomb excitation data analysis codes; gosia 2007 - Physics and ...

12 GAMMA DETECTION EFFICIENCY CODE: GREMLINAlexander KavkaUniversity of RochesterThe FORTRAN program GREMLIN (“Gamma-Ray Efficiency Measurement and Line INtensity calculation”)was developed at Rochester in 1987 by Alexander Kavka. The purpose is to simplify the routineprocedure of γ-ray detector efficiency calibration and detection efficiency correction of measured peak areasfor deexcitation γ-ray yields following Coulomb excitation.GREMLIN can perform two separate tasks:1) Least-squares fit ofaγ-ray detection efficiency-calibration function to a set of peak areas from γ-raycalibration spectra.2) Calculation of detection-efficiency corrected γ-ray intensities from peak areas, using the fitted efficiencyfunction for the Doppler shift corrected γ-ray energy.The functional form of the dependence of detection efficiency on γ-ray energy is factored into terms thatseparately account for γ-ray absorption, high and low energy dependence, and electronic thresholds in orderto obtain well-behaved functions that do not exhibit pathological behaviour such as at K-edges.GREMLIN is an essential component of the GOSIA suite of Coulomb excitation analysis codes and canbe used in either of two modes. One approach is to use GREMLIN to correct the raw peak areas of theobserved deexcitation γ-rays to account for the γ-ray detector efficiency at the appropriate Doppler-shiftedenergy. These corrected yields then are input as the data to be fit by GOSIA. The second approach is to usethe GOSIA option OP,RAW which allows input to GOSIA of the raw, i.e. not detector efficiency corrected,γ-ray yields. The parameters for the γ-ray detection efficiency function, as determined by the GREMLINleast-squares fit, are used by OP,RAW to detector-efficiency correct the raw yields input to GOSIA.The code GREMLIN is interactive, and its prompts and questions are hopefully sufficient to guide theuser. Therefore, this memo provides no real input instructions, with one exception: it describes the structureof the input files containing the calibration points.12.1 Option 1: EFFICIENCY CALIBRATION1.1 Input of calibration pointsA maximum of 500 calibration points can be entered, grouped in up to 9 independently normalized datasets. Typically, these will originate from runs with different calibration sources, but there can just as wellbe several sets from the same source. If there is more than one data set, the code will automatically fitnormalization parameters.GREMLIN will ask for calibration points for each data set separately. For each set the input can befrom a disk file or from the keyboard, and consists of one record for each calibration line. A record looks asfollows:E, I, ∆I, A, ∆Awhere E is the γ-ray energy, I ± ∆I the tabulated relative intensity, and A ± ∆A the measured peak area.Note that two data sets cannot be in one file.However, the input is simplified in the case of 152 Eu or 182 Ta sources, because the energies and intensitiesof major 152 Eu and 182 Ta transitions are stored in DATA statements in the program. These values weretaken from R.A. Meyer: Multigamma-Ray Calibration Sources (Lawrence Livermore Laboratory 1978). Therecord format is thenA, ∆AIf keyboard input was chosen, the code will display each tabulated energy and intensity and ask for the areaand error. In an input file, the 152 Eu or 182 Ta lines must be given according to the following table:190