Analysis of mini-STRIKE diagnostic calorimeter data by the transfer function technique

STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic which will be used to characterize the SPIDER beam, by measuring beam uniformity, beam divergence and stripping losses. STRIKE will be directly exposed to the beam and will be composed of 16 panels (396mm x 160 mm x 20 mm each), corresponding to the beam (beamlet groups) structure [1] . According to SPIDER design, STRIKE tiles will be observed from behind and the beam features will be inferred from the temperature increase of the rear side measured by infra-red cameras. As the use of 1D-CFC tiles allows to distinguish beamlets [3] or beaml et -like structures [2] , the standard analysis performed on the thermal images is based on applying a multi-peak 2D fit to the acquired temperature map, in which a Hubbert function is associated to each peak. Both in terms of resolution and time required by calculation it would be helpful to determine from the 2D map of temperature a map of the power flux impinging on the front side. This contribution describes a method to perform this action which is based on the transfer function technique and allows a fast analysis by means of the FFT algorithm. The efficacy of the method has been tested both on simulated data and experimental data acquired by mini- STRIKE, the prototype version of the calorimeter tested at IPP and NIFS ion source test stands. In all cases the energy flux features are well reproduced and beamlets are well resolved [4] . In addition, the comparison between the results of the standard analysis and those obtained with the transfer function method proved the diagnostic capability of this data processing approach. Limits and restrictions of the method are also discussed, providing strategies to handle issues related to signal noise and digital processing.