Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The AMS-02 Tracker

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The AMS-02 detector is based on a large acceptance (~0.5 m ² sr) and high sensitivity spectrometer, composed of a super-conducting magnet and a silicon tracking device (Tracker). An Anti-Coincidence Counter placed inside the inner bore of the magnet allows to reject particles entering the Tracker laterally, outside the main acceptance. A Star Tracker has been added to the AMS-02 set-up to ensure accurate knowledge about the instrument orientation, since the ISS attitude is rather variable.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The superconducting magnet is cooled by evaporating liquid helium and has a reservoir for about three years of operation without refill. Its dipolar field, normal to the aperture of the magnet, is based on a magic ring configuration of race track coils around a pair of Helmholtz coils. With a field strength of 0.8 Tesla at the centre it extends the rigidity range for charged particles up to few TV.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone June 14, 2004 Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland In order to remove the heat dissipation generated inside the magnet by the Tracker front-end electronics a dedicated Thermal Control System has been developed. It is based on a mechanically pumped two-phase loop with carbon dioxide as working fluid.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The Tracker is built with close 2500 double sided silicon microstrip sensors, which allow to measure two coordinates with a single detector, reducing thus the material budget. The AMS-01 Tracker has been the first application in space of the high precision silicon technology developed for position measurements in accelerator experiments. The high modularity, low voltage (<100 V), and gas-free operation of the device is well suited to operation in space. The 1998 shuttle test flight has proven both the successful adaptation of the technology to the space environment and the feasibility of large area detectors.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The n-type, high resistivity (> 6 k Ω ) sensors are biased with the punch-through technique and p + blocking strips, implanted on the n-side, are used to minimize the influence of surface charge on the position measurement obtained from the ohmic side. The sensor design uses capacitive charge coupling with implantation (readout) strip pitches of 27.5 (110) µ m for the p-side and 52 (208) µ m for the n-side. The finer pitch p-side strips measure the bending coordinate and the n-side strips measure the orthogonal coordinate, achieving a tracking resolution of 10 µ m and of 30 µ m respectively. The measurement of specific energy loss, dE/dx proportional to Z ², in the silicon allows independent nuclei identification in the Tracker.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland AMS-02 silicon sensors characteristics Dimensions 7.2 cm × 4.1 cm Thickness ~300 µm Active width p-side ~70.5 mm Strip pitch p-side 27.5 µm Num. of p-strips 2568 Readout pitch p-side 110 µm Num. of p-side readout strips 640 Active width n-side ~39.8 mm Strip pitch n-side 104 µm Num. of n-strips 384 Readout pitch n-side 208 µm Num. of n-side readout strips 192

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The silicon sensors will be arranged in 192 ladders. The ladder is made of variable number of silicon sensors (from 7 to 15) with daisy chained strips to increase the detection surface while using a limited readout. To connect the n-side strips a Upilex foil with copper strips is used to transmit the signal to the front-end electronics.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland Two ladders ready to be installed:

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The ladders will be installed in eight layers of ~1 m² each on five planes of an ultra-light support structure.

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland Installing ladders on plane:

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland The first layer assembled:

Third International Conference on Frontier Science Villa Mondragone – Monteporzio Catone Physics and Astrophysics in Space June 14, 2004 Mercedes Paniccia University of Geneva - Switzerland Until now 80% of ladders have been produced with the effort of several institutions involved in the AMS-02 Tracker collaboration (University of Geneva, INFN-Perugia, ETH-Zurich, University of Bucarest, University of Turku, Skobeltsyen INP, Southeast University and an industrial firm in Italy). Three out of eight layers have been fully equipped with ladders at University of Geneva. The Tracker assembly is foreseen to be completed by In the meantime an extensive series of tests have been performed to verify the performance of the AMS-02 silicon Tracker: results will be presented by next speaker P. Zuccon.