Students*: Dumitru Irina, Giubega Lavinia-Elena, Lica Razvan, Olacel AdinaCoordinators**: Dr. Slepnev Roman, Dr. Parfenova Yulia

* Faculty of Physics, University of Bucharest** Flerov Laboratory of Nuclear Reactions, JINR, Dubna

1) Creating the geometry of the detectors in ROOT for efficiency estimates with Monte-Carlo simulations

2) Measurements of dead-layer of the Silicon detectors used for studies of 8He(t, p)10He

The geometry of the experimental setup is studied with the example of 8He(t, p)10He reaction.

q The detectors setup was in accordance with the theoretical predictions for the angles of the momentum of the reaction products. The efficiency is important. We build this geometry in order to make Monte-Carlo simulations of events, wich would permit us to calculate the efficiency of registration.

The proton telescope consisted ofone 300 μm thick annular Si detector. The activeareas of this detector had the outer and inner diameters of 82 mm and 32 mm, respectively. The proton telescope was installed100 mm upstream of the target and covered an angularrange of 171◦–159◦ in lab system. The detector was segmentedin 16 rings on one side and 16 sectors on the other side. This construction serves for identifying the angle and coordinate of the particle. With this information we can restore the full kinematics of the reaction.

Zero angle telescope for the 8He detection was installedon the beam axis at a distance of 25 cm from the tritium target .The telescope included six squared (60 × 60 mm) 1 mm thick detectors.The first detector of the telescope was segmented in16 strips in vertical directions. All other detectorsin the telescope were segmented in 16 strips in horizontal direction.

Silicon detectors were used for the capture of 8He nuclei. One of their drawbacks is the presence of a layer at the surface in which the radiation is partly absorbed but no electric signal is produced. This region is called dead layer.

If we know the thickness of the dead-layer, we can determine the energy lost in the layer and correct the output.

For determining the dead-layer of the detectors, we used a alpha-particle source in two different setups (0⁰ and 45⁰) and analyzed the spectra obtained

The peaks were shifted and by measuring the relative energy shifting we could determine the thickness of the DEAD-LAYER.

We have 2 sources of errors:

*) we approximated the energy loss trough the detector to be linear

*) we have a statistical error for the gaussian fit (of about 2 channels). This corresponds to error of 4%.

0 Degrees

45 Degrees

The final geometry

The estimated value for the thickness of the dead-layer is 2.16±0.10 µm

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