Hello all,
I am a novice user of TOPAS and is now trying to fit peak intensity of a set of TOF data.

The aim is to extract peak shape function for individual peak and to investigate the variation with d/tof.
I was following the method from this tutorial for my task

http://topas.dur.ac.uk/topaswiki/doku.php?id=time_of_flight_tof_peak_fitting

The refined profile parameters however are the same for different peaks, although I have put them into different xo_Is and they show up as individual parameters though in the error matrix they do display.

The fitted errors for peak intensity and position also show the same behavior which is very strange…

Can anyone comment on this? Or maybe share with me a .inp file, where individual peak fitting for TOF is successfully?

Code as follows,

r_wp 9.59706967 r_exp 1.51447607 r_p 5.88623739 r_wp_dash 33.9325396 r_p_dash 39.262383 r_exp_dash 5.35476151 weighted_Durbin_Watson 0.12032738 gof 6.33689092
do_errors
iters 100000
no_LIMIT_warnings
chi2_convergence_criteria 0.00001

#define Si_POWGEN_bank1

#ifdef Si_POWGEN_bank1
TOF_XYE (ALL_PG3_37849-1.xye,= Yobs_dx_at(Xo).5;)
TOF_LAM(0.001)
scale_pks = D_spacing^4;
start_X 8000
finish_X 90000
bkg @ 61.3845949`_0.212261848 -0.571076017`_0.385933515 -0.521210336`_0.337763886 -1.41751975`_0.310779123 -0.322338134`_0.249688129 -0.830061073`_0.181707633
neutron_data
local !zero -2.16008 'don't refine
local !dif_c 22592.70827 'don't refine
local !dif_a -8.28523 'refine if necessary
pk_xo = zero + dif_c D_spacing + dif_a D_spacing^2;

str

scale scal_f1 81.9708166`_0.6399
space_group Fd-3m:2
Cubic(5.431178)
site Si num_posns 8 x 0.125 y 0.125 z 0.125 occ Si 1 beq beqSi 0.00388`_0.00830
TOF_PV(si_fwhm, 340.82370`_4.74739, si_fwhm_lor, 1`_0.019429912, dif_c)
'TOF_Exponential(@, 100, ,0, 1, dif_c, -)
'TOF_Exponential(@, 100, @, 100, 4, dif_c, +)

xo_Is xo @ 30659.1137`_6.33689092 update = Val + Rand(-1, 1) Change; I @ 5702.32662`_6.33689 max 30000 TOF_PV(@, 219.79170`_6.33689 max 1000, @, 0.5`_6.33689092, dif_c)
xo_Is xo @ 36972.9316`_6.33689092 update = Val + Rand(-1, 1) Change; I @ 11758.92474`_6.33689 max 30000 TOF_PV(@, 219.79170`_6.33689 max 1000, @, 0.5`_6.33689092, dif_c)
xo_Is xo @ 43350.4812`_6.33689092 update = Val + Rand(-1, 1) Change; I @ 11979.38159`_6.33689 max 30000 TOF_PV(@, 219.79170`_6.33689 max 1000, @, 0.5`_6.33689092, dif_c)
xo_Is xo @ 70760.828`_6.33689092 update = Val + Rand(-1, 1) Change; I @ 4000.64690`_6.33689 max 30000 TOF_PV(@, 219.79170`_6.33689 max 1000, @, 0.5`_6.33689092, dif_c)

Thanks u all for the help!