Balog, T.

Heuser, J. M.

Sorokin, I.

GSI Repository

Performance of a first prototype module for the CBM Silicon Tracking System∗T. Balog1,2, I. Sorokin3,4, and J. M. Heuser11GSI, Darmstadt, Germany; 2Comenius University, Bratislava, Slovakia; 3Goethe University Frankfurt a.M., Germany;4KINR, Kiev, UkraineThe building block of the CBM Silicon Tracking Sys-tem is a detector module, a functional unit of one or sev-eral daisy-chained double-sided silicon microstrip sensors,read-out cables and front-end electronics. Ten modules willbe located on a detector ladder. Several ladders build up aSTS tracking station [1].A first prototype module comprises CBM01 double-sided sensor with 1024 channels on both sides. On everyside 1/8 of the channels are read out via low-mass ca-bles connected to two front-end boards each hosting onen-XYTER chip.Figure 1: Photo of the prototype module.MeasurementsThe noise performance of the system was determined us-ing external triggers where baselines of the read-out elec-tronics were triggered. Main noise source in the strip sil-icon detectors with cables is interstrip capacitance whichwas determined for all three prototypres (Table 1). Inthe analysis the gaussian fits of the baseline distributionswere calculated and their standard deviations (σ) taken asa measure of the noise in the channels. According to then-XYTER ADC calibration the noise is then expressed inequivalent noise charge (ENC) - amount of charge seen bythe read-out electronics (Figure 2) [2].Afterwards the charge collection efficiency for all threedemonstrators was measured using a 241Am source withSilicon detector. It’s 59.5 keV gamma line correspondsto 114 ADC units. As seen in Figure 3 signal amplitudedepends on the length of the cable connected to sensor.Within the measured prototypes the charge collection ef-ficiency was above 85%.∗Work supported by EU-FP7 HadronPhysics3, Helmholtz Interna-tional Center for FAIR and EU-FP7 MC-PAD.Length of read-out cable Interstrip capacitance[cm] [pF]10 cm 16.5 pF20 cm 22.1 pF30 cm 26.8 pFTable 1: Measured interstrip capacitances of prototypes.Figure 2: Noise performance of the prototype modules as afunction of read-out cable length.Figure 3: 241Am spectra from the prototype modules.ConclusionFor efficient track recontruction with the STS the noiseof the read-out module is required to be below 4 ke−. Themeasurements with the prototype module achieved a noiselevel well below 3 ke− (measure of 3σ).According to the measured noise and the charge col-lection efficiency the expected signal-to-noise ratio forminimum ionizing particle in the prototype modules isabove 20.References[1] GSI Scientific Report 2011, p.22[2] I. Sorokin et al.: Transconductance calibration of n-XYTER1.0, This reportGSI SCIENTIFIC REPORT 2012 PHN-NQM-EXP-2453

Performance of a first prototype module for the CBM Silicon  Tracking System

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Performance of a first prototype module for the CBM Silicon Tracking System

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