Fitting Ba-133 data from 32 coarse grid positions (20 Feb 2004)

We have developed a spectral model for Ba-133 data, which is composed of the multi-mutau-model (based on 36 sets of measured mutau products) and the exponential tail (only for 31 and 35 keV lines). It is fitted fairly well with one of the coarse grid run data. Here, we will apply the model to more data from 32 coarse grid runs, and try to

1. figure out how well the model fits the data obtained with different source positions,
2. examine how much the parameters correlate with source angle,
3. find out a formula which represents an absorption efficiency.

Spectral Model

The current model is composed of the multi-mutau-model (based on 36 sets of measured mutau products) and the exponential tail (only for 31 and 35 keV lines). Though the calibraion data are processed with a gain of 4.0 bins/keV, the mutau-model gives slightly non-linear peak positions due to the different interaction depth for differet energy lines. We therefore adjust it as a power-law function ( gain1 * E^gain2 ). The normalization parameters are represented as photon flux at the center of the detector array in units of photons/sec/cm^2. The fitted normalizations do not perfectly become proportional to the branching ratio of radio active source. This is mainly due to an absorption by passive material between source and detector. Therefore, we let the normalizations vary independently for the moment. We hope to find out some formula which represent the absorption efficiency as a function of energy and angle.

1. sigma         : energy resolution [channel]
2. gain1         : gain1 * E^gain2 [channel/keV]
3. gain2         : 
4. norm31        : normalization of 31 keV line (main peak + exponential tail) [photons/sec/cm^2]
5. norm35        : normalization of 35 keV line (main peak + exponential tail) [photons/sec/cm^2]
6. norm53        : normalization of 53 keV line (mutau model) [photons/sec/cm^2]
7. norm81        : normalization of 53 keV line (mutau model) [photons/sec/cm^2]
8. tail_length   : exp( (E-main_peak)/tail_length ) [channel]
9. tail_ratio    : the ratio of counts which comes into exponential tail from photo-absorption events

Fitting Results


.cg06_x_ba133_030304_8_c_ff.pha	cg08_x_ba133_030304_10_c_ff.pha	cg09_x_ba133_030304_11_c_ff..pha

cg10_x_ba133_030304_12_c_ff.pha	cg11_x_ba133_030304_13_c_ff.pha	cg12_x_ba133_030304_14_c_ff.pha

cg13_x_ba133_030304_15_c_ff.pha	cg15_x_ba133_030304_17_c_ff.pha	cg16_x_ba133_030304_18_c_ff.pha

cg17_x_ba133_030304_19_c_ff.pha	cg18_x_ba133_030304_20_c_ff.pha	cg19_x_ba133_030304_21_c_ff.pha

cg20_x_ba133_030304_22_c_ff.pha	cg21_x_ba133_030304_23_c_ff.pha	cg23_x_ba133_030304_25_c_ff.pha

cg24_x_ba133_030304_26_c_ff.pha	cg25_x_ba133_030304_27_c_ff.pha	cg31_x_ba133_030304_33_c_ff.pha

cg33_x_ba133_030304_35_c_ff.pha	cg34_x_ba133_030304_36_c_ff.pha	cg35_x_ba133_030304_37_c_ff.pha

cg36_x_ba133_030304_38_c_ff.pha	cg37_x_ba133_030304_39_c_ff.pha	cg38_x_ba133_030304_40_c_ff.pha

cg39_x_ba133_030304_41_c_ff.pha	cg_x_ba133_030304_3_c_ff.pha	cg_x_ba133_030304_4_c_ff.pha

cg_x_ba133_030304_5_c_ff.pha	cg_x_ba133_200_21_030306_1_c_ff.pha	cg_x_ba133_200_21_030306_2_c_ff.pha

cg_x_ba133_200_21_030306_3_c_ff.pha	cg_x_ba133_200_21_030306_4_c_ff.pha

Correlation between fitted parameters and source angle

reduced chi-squared, sigma, and gain parameters

norm31

norm35

norm53

norm81

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