NICE prototype overall detection efficiency

The plots below were produced using the following procedure:

  1. scaling the TOF spectra (those with beam and background) to counts per second
  2. subtracting background from each TOF spectra with beam (some interpolation was needed as the background spectra were taken using a coarser grid in the alpha/theta parameter space.
  3. scaling the TOF spectra to counts per primary particle (using the beam current)
  4. fitting H,C,O peaks using a gaussian/lorenzian-fit function
  5. because of pointing problems (the surface moves easily out of the FOV of the beam when alpha/theta movements are made as the theta axis of rotation was offset by 25mm) for each alpha-position (the position of the linear table) the maximum intensity value of all theta angles was taken for the further analysis: Intensity_max_H,C,O(alpha_position) = max(Intensity_H,C,O(alpha_position,theta-position). Basically in all cases the maximum value chosen at a specific alpha position was taken from the same spectra for each species. This makes it reasonable that the reduced count rate at certain positions was indeed due to pointing problems. Furthermore I do not expect a significant dependence of the ionization yield of the angle of incidence within the theta range and the surfaces used. One drawback of this procedure is that the sputtered particle fraction might be overestimated. The resulting plots may be found following the link in the "alpha/theta scan" sections below
  6. from the Intensity_max_H,C,O data the CODIF entry slit width was deconvolved.
  7. separation of sputtered particles: all particles not belonging to the primary species were considered to be sputtered. The sputtered fraction of the species on the primary beam was estimated using the energy (alpha-position) distribution of the sputtered other particles.
  8. integration of the counts of all species converted and sputtered over the whole alpha range.
  9. in some plots Bern data taken in spring 2001 was included. Note the good agreement between the Bern and the Denver data.  Empirical fits to some of the efficiencies were added to be able to comapre the conversion and sputter data to models taken from literature. 

Some additional notes:

  • The error bars include only the average errors from fitting the TOF spectra and from the in some cases limited resolution of the current measurements in the logfiles. More detailed errors and also further sources of errors (like the interpolated background) will be included later. The values shown are a slightly pessimistic estimate.
  • Not included in the error bars are errors arising from single bad data points that resulted in removal of counts and thus worsend the counting statistics (is the case for about 10% of the data used). This and more will be included in a later data analysis.
  • The carbon fractions are only upper limits as it was difficult to separate them from oxygen because of the overlapp of the peaks. 
  • The values shown in the plots below indicate the overall detection efficiency of the prototype instrument calculated as detected particles per incident neutral particle hitting the conversion surface.

The results from the Bern measurements in 2001 are also included in this plots.

Summary for all invetigated surfaces

This plot contains all the empirical fits to the detection efficiencies. For details see the plots for each individual surface below. All available data from Bern and Denver measurements was combined.

summary_nice_all.pdf
summary_nice_all.ps
summary_nice_all.gif

CVD  diamond conversion surface

Primary particle: neutral H

h_diamond_nice_all.pdf
h_diamond_nice_all.ps
h_diamond_nice_all.gif

Primary particle: neutral O

This plots include the Bern results from spring 2001.

o_diamond_nice_all.pdf
o_diamond_nice_all.ps
o_diamond_nice_all.gif

MgO conversion surface

Primary particle: neutral H

h_mgo_nice_all.pdf
h_mgo_nice_all.ps
h_mgo_nice_all.gif

Primary particle: neutral O

This plots include the Bern results from spring 2001.

o_mgo_nice_all.pdf
o_mgo_nice_all.ps
o_mgo_nice_all.gif

Tungsten (LENA) conversion surface

Primary particle: neutral H

h_tungsten_nice_all.pdf
h_tungsten_nice_all.ps
h_tungsten_nice_all.gif

Primary particle: neutral O

o_tungsten_nice_all.pdf
o_tungsten_nice_all.ps
o_tungsten_nice_all.gif

BaZrO3 conversion surface

Primary particle: neutral O

o_bazro3_nice_all.pdf
o_bazro3_nice_all.ps
o_bazro3_nice_all.gif