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Position sensitive monolithic silicon telescopes

Catania University. Position sensitive monolithic silicon telescopes.

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Position sensitive monolithic silicon telescopes

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  1. Catania University Position sensitive monolithic silicon telescopes F. Amorini, V. Sipala, G. Cardella, B. Carbone, L. Cosentino, A. Di Pietro, G.Fallica, P. Finocchiaro, A. Pappalardo, A. Piazza, N. Randazzo, V. Russo, C. Scirè, S. Scirè, G.Valvo, C. Boiano, U. Emanuele, E. La Guidara, M. Trimarchi

  2. Why a new position sensitive detector • Compact detection systems and low particles identification thresholds, together with good angular resolution and high granularity, are nowadays requirements to perform complete studies for nuclear reactions induced by stable and radioactive beams at low and intermediate energies • It is very difficult to obtain very compact geometries with conventional identification techniques (DE-E), when thresholds lower than 1 MeV/A are required • Alternative techniques (i.e. pulse shape analysis) allows charge identification of the ions with the use of a single detector, but shows rather high identification threshold per nucleon, increasing with Z F. Amorini – INPC 2007 Tokio June 3-8 2007

  3. State of the art Gas detectors: often used as first stage in DE-E devices, allows adjustable thresholds, provide position information, but they are usually very bulky Silicon detectors: can be designed in different shapes, but they cannot be built with thickness below 5 mm and are very fragile and expensive Silicon strip detectors: provide only one coordinate with N electronic channels per detector Double layer silicon detectors: provide the two coordinates with 2N electronic channels, but are difficult to be built and mounted due to the presence of contacts on both sides Silicon drift detectors: calibration very sensitive to the temperature and slow time response F. Amorini – INPC 2007 Tokio June 3-8 2007

  4. Monolithic silicon telescopes The advantages of easy handling of a silicon device, without the problem of fragility, can be obtained building a telescope with a very thinDE stage implemented directly on the same structure of the E stage. • p+ wells realized with a boron low energy implantation followed by high temperature (1050 °C) diffusion up to 2mm depth • p+ region acting as common ground electrode for the two stages obtained via high energy (900 keV) boron implantation on an n- bulk of 5000  cm resistivity F. Amorini – INPC 2007 Tokio June 3-8 2007

  5. The strip detector The best compromise between performances and reduced capacitance 5 independent E strips having common E stage Common ground contact Single E strip Two modules mounted on a ceramic package and connected to commercial charge preamplifiers, assembled on compact boards working under vacuum A.Musumarra et al. NIM A 409 (1998) 414 F. Amorini – INPC 2007 Tokio June 3-8 2007

  6. Performance of monolithic telescopes Stable beam induced reactions Radioactive beam induced reactions 40Ca+48Ca 10MeV/A 13N+9Be 45 MeV Besides good charge identification, it showed up the possibility to achieve an efficient β suppression F.Amorini et al, NIM A 550 (2005) 248 F. Amorini – INPC 2007 Tokio June 3-8 2007

  7. E-signal DE-signal “Induction” peak + + + + + + + - - - - - - The induction effect During the performed experiments it showed up the presence of some “noise”, in strips not directly fired + + + + + Due to the finite resistance of the implanted ground electrode that can be of the order of some kW (see A.J.Kordyasz NIM A 530 (2004) 87, for details) the charge created in the E stage changes the electric field of the DE stage and induces a fast signal larger than the real signal. F.Amorini et al, NIM B (Proc. Supp.) 550 (2006) 227 F. Amorini – INPC 2007 Tokio June 3-8 2007

  8. 5 4 3 2 1 Investigation of the induction signal The amplitude of the induction on strip 5 (the farthest from the ground contact) is measured when center of strips 1 to 5 are irradiated by a standard a source The results showed a dependence of the induction signal from the position of the impinging particle F. Amorini – INPC 2007 Tokio June 3-8 2007

  9. The new position sensitive monolithic detector Exploiting the induction effect we designed a new monolithic telescope capable to provide position information y 16 strips 8 x 0,5 mm implanted on a common E stage Starting idea: x coordinate is given from the strip number Y coordinate is extracted from the induction signal along the strip . . . . . . x Ground contact F. Amorini – INPC 2007 Tokio June 3-8 2007

  10. 1 mm 130 mm Test of the prototype The detector was irradiated by means of the micro-beam facility of the Laboratori Nazionali del Sud (LNS). The beam spot was 50 mm Each strip was explored by hitting it by a 30 MeV 12C beam on 8 points, 1 mm spaced, along the vertical direction. At fixed vertical positions with an interval of 2 mm, it was explored the horizontal behaviour of the strips by irradiating two more points at ±130 mm from the centre. F. Amorini – INPC 2007 Tokio June 3-8 2007

  11. Strip 9 Strip 7 Analysis of the induction signal • The induction signal depends strongly from the irradiation point, even if the response function appears to be not linear. • As can be seen from the separation of the horizontal points, the x resolution is well below the 500 mm of the dimension of the strip. • The sensitivity in both direction deduced from the measured positions is better than 5 mm F. Amorini – INPC 2007 Tokio June 3-8 2007

  12. Ions identification a source 12C+14N 54 MeV The position sensitive prototype showed the same good performance of the standard monolithic detector, with good identification for both light and heavy ions F. Amorini – INPC 2007 Tokio June 3-8 2007

  13. Conclusions and Outlook • The new monolithic telescope is capable to give the position of the impinging particle, together with energy and time. It showed very good identification performances and a sensitivity to the position up to 5 mm, comparable with existing position detector, offering as well the possibility to be arranged in various configuration due to its reduced size • Further work is needed to completely characterize the position response of the detector and to develop an algorithm to extract the position information without reading all the channels • An integrated electronics is under realization, to read E, DE, X and Y signals from each strip, minimizing the number of readout channels for the device • On the basis of the achieved results, we are studying new layouts to build larger devices, useful in multidisciplinary applications (imaging, autoradiography) F. Amorini – INPC 2007 Tokio June 3-8 2007

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