SIDDHARTA Detector

 

 

 

Silicon Drift Detectors (SDD) were originally proposed by Emilio Gatti, Politecnico di Milano, and Pavel Rehak, BNL, USA, as an improved alternative to silicon microstrip detectors in high energy physics applications. Radiation hardness, spatial and time resolution, compactness, as well as the easiness to be interfaced to fast readout systems made them a leading detector in the field. Few years after the first applications, the Silicon drift detectors were developed as an X-ray spectroscopic tool, due to a series of characteristics impossible to implement (all together) in any other X-ray detector:

 

-         high efficiency (near to unity) in a wide range of X-ray energies (from few hundreds eV to about 15 keV) due to the relatively thick sensitive layer, typically few hundred micron;

-         good energy resolution, achievable with a minimal cooling reached by Peltier coolers, which eliminates the need to employ liquid Nitrogen or expansion cryostats;

-         high speed of operation (104 to 106 particle/s, according to the requested precision and topology);

-         low internal electromagnetic background with respect to other thicker (crystal) detectors;

-         good energy separation between minimum ionizing particles and photons;

-         low EMI noise due to the integrated front-end transistor;

-         possibility of choosing the topology according to the needs of the experiment.

 

The timing properties of the SDDs have not been up to now exploited in the field of X-ray spectroscopy. The goal of our project is to take advantage of both energy and time resolution of spectroscopic SDDs and to enlarge the area of usage of these detectors in triggered applications. Since the exotic atom transition is a rare event, many triggers will be delivered before a good event will be registered. This will enlarge the time acceptance window by more than three orders of magnitude. By assuming a window of the order of 1 ms and by assuming that, in average, only 1 detected kaon over 103 ends out in a detected kaonic hydrogen X-ray. A S/B ratio of the order of 1 can be achieved in experiment with kaonic hydrogen and of the order of 1/10 with kaonic deuterium, allowing to perform a percent level precision measurement.