M. Agari

Production of the LHCb Silicon Tracker Readout Electronics

A. Vollhardt, A. Bay, B. Carron, P. Fauland, R. Frei, S. Jimenez-Otero, A. Perrin, M.T. Tran, J. van Hunen, K. Vervink, M. Agari, C. Bauer, J. Blouw, W. Hofmann, K.T. Knopfle, S. Lochner, M. Schmelling, B. Schwingenheuer, N. Smale, B. Adeva, D. Esperante, C. Lois, P. Vazquez, R.P. Bernhard, R. Bernet, J. Gassner, S. Kostner, F. Lehner, M. Needham, O. Steinkamp, U. Straumann, D. Volyanskyy, H. Voss, A. Wenger

The silicon tracker of the LHCb experiment

LHCb is one of the experiments of the Large Hadron Collider at CERN, dedicated to B-physics and CP-violation measurements. To fully exploit the physics potential, a good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large read-out pitch and long strips will be used for the LHCb inner tracker after the magnet and the trigger tracker station in front of the magnet. We report here about the design of the silicon tracker, test beam results and the electrical tests foreseen during module production.

SEU Robustness, Total Dose Radiation Hardness and Analogue Performance of the Beetle Chip

The Beetle is a 128 channel readout chip for silicon strip detectors in LHCb. In addition to the pipelined readout path known from the RD20 architecture which can be used either in analogue or binary mode, the Beetle features an additional prompt binary readout path, used for the LHCb pile-up veto counters and a triple-redundant layout of the control logic. It is manufactured in commercial 0.25μm CMOS technology using radiation hard design techniques. In addition to a total dose irradiation with X-rays, an SEU irradiation test with 65 MeV protons was performed with Beetle1.3. The results of this test are presented together with new results from the Beetle versions 1.3, 1.4 and 1.5, which were submitted in the Beetle ER engineering run in May 2004. I. The Beetle Chip Architecture The Beetle [1] is an analogue pipelined readout chip and implements the RD20 front-end architecture [2]. For a fast trigger decision it provides a comparator with prompt binary output signals. Using the comparator output signals instead of analogue front-end signals, the Beetle can alternatively operate in a binary pipelined mode. Figure 1 shows a schematic block diagram of the latest versions Beetle1.2 to 1.5. The chip integrates 128 channels. Each channel consists of a low-noise charge sensitive preampli er, an active now at Stanford Linear Accelerator Centre ynow at Continental Teves AG znow at Dialog Semiconductor GmbH now at Fujitsu Mikroelektronik GmbH CR-RC pulse shaper and a bu er. For capacitive loads 50 pF the chip achieves rise times 25 ns and spillover of 30% of the maximum at 25 ns after the peak, suitable for operation within the LHCb experiment. The chip provides two di erent readout paths. For the binary readout the front-ends output couples to a comparator which features invertable outputs to detect input signals of either polarity and individually adjustable threshold levels. Four adjacent comparator outputs are logically ORed, latched, multiplexed by 2 and routed o the chip via low voltage di erential signaling (LVDS) ports at 80 MHz. The pipelined readout path can operate in either a binary mode by using the comparator outputs or an analogue mode by sampling the front-end bu ers output with the LHC bunch-crossing frequency of 40 MHz. The sampled amplitudes are stored in an analogue memory (pipeline) with a programmable latency of at maximum 160 sampling intervals. This is combined with an integrated trigger bu er of 16 stages. Upon a trigger the corresponding signals stored in the pipeline are transferred to the multiplexer via a resettable charge sensitive ampli er. The number of active output ports is con gurable and allows a readout time of at minimum 900ns per event. The output of a sense channel is subtracted from the analogue data to compensate common mode e ects. On-chip digital-to-analogue converters (DACs) with a resolution of 8 bits generate the bias currents and control voltages. For test and calibration purposes, an adjustable charge injector is implemented on each channel. All bias settings and con guration parameters, e.g. trigger latency, readout mode and readout speed, can be programmed and read back via a standard IC-interface [3]. All digital I/Os, except for the IC-lines and the daisy chain ports, use LVDS signals. The Beetle is designed in a commercial 0.25μm CMOS technology and has a die size of 6:1 5:4mm. The pitch of the analogue input pads is 40.24μm. If no prompt readout is required, the chips can be mounted side-by-side, since no connections to the top and bottom side of the chip are required. This allows an overall pitch of 50 μm matching the readout pitch of typical high resolution silicon strip detectors. In case of the silicon vertex detector, the readout chip will be positioned only 5 cm from the LHC beams, which means that the Beetle has to be radiation hard. The chip is designed to withstand a total dose in excess of 10 Mrad (100 kGy) by taking the following design measures [4]: forced bias currents are used in all analogue stages instead of xed node voltages; enclosed gate structures for NMOS transistors suppress increasing leakage currents under irradiation; a consistent use of guard rings minimises the risk of Single Event Latchup (SEL) [5]. II. Chip Performance Most analogue measurements performed on the previous versions of the Beetle chip have been repeated with Beetle1.3. Measurements of pulse-shapes gain and noise (tab. 1) were conducted, all reproducing the results presented in [6] and [7] very well. Also a comparison of the equivalent noise charges of Beetle1.3 with the results from the Beetle FE 1.1 frontend-only test chip was performed. It showed an only marginal degradation of the noise performance due to the stages of the pipelined readout, corresponding to a 50 e rise in the o set parameter. Table 1: ENC of the Beetle1.3 chip in pipelined operation mode as a function of the Vfs (shaper feedback) control voltage. Vfs Equivalent Noise Charge 0mV 547:7 e + 52:64 e =pF 100mV 539:1 e + 51:89 e =pF 400mV 542:8 e + 49:38 e =pF 1000mV 465:1 e + 45:22 e =pF III. The Beetle ER engineering run A Production Readiness Review (PRR) for the Beetle chip was held at Heidelberg on the 20 of April 2004. It concluded that Beetle1.3 ful ls the requirements of the VeLo and ST detectors, but needs an improved Vertex Locator Silicon Tracker, consisting of Trigger Tracker (TT) and Inner Tracker (TT) detectors discriminator for the application in the VETO. Thus it concluded to place two or three versions of the chip on the reticle for an engineering run. In case of three versions in equal quantities, a subsequent production run would result in 12500 chips/version, while only 3500 are needed to equip the experiment, leaving enough margin for production yield and spares. Therfore it was later on decided to place equal quantities of any chip version on the reticle of the engineering run. Although the Beetle1.3 ful ls the requirements of VeLo and ST, an attempt was made to x the remaining minor problems along with the redesign of the comparator needed in the pile-up VETO. Those include a wrongly encoded pipeline column number parity bit in consecutive readout, some cross talk between the readout lines of the pipeline, and baseline variations between consecutive and non-consecutive event readouts. The foreseen modi cations were categorized into low risk and high risk, and submitted in two di erent designs, in order to maximize the probability of receiving a working chip that satis es all requirements by VETO, VeLo and ST.

Production and Quality Assurance of Detector Modules for the LHCb Silicon Tracker

The LHCb experiment, which is currently under construction at the Large Hadron Collider~(CERN, Geneva), is designed to study CP violation and find rare decays in the B meson system. To achieve the physics goals the LHCb detector must have excellent tracking performance. An important element of the LHCb tracking system is the Silicon Tracker, which covers a sensitive surface of about 12~m2 with silicon microstrip detectors and includes about 272k readout channels. It uses up to 132~cm long detector modules with readout strips of up to 38~cm in length and up to 57~cm long Kapton interconnects in between sensors and readout hybrids. The production of detector modules has been completed recently and the detector is currently under installation. A rigorous quality assurance programme has been performed to ensure that the detector modules meet the mechanical and electrical requirements and study their various characteristics. In this paper, the detector design, the module production steps, and the module quality assurance programme are briefly described.

LHCb Silicon Tracker Performance Studies

LHCb is one of the experiments for the Large Hadron Collider at CERN and is dedicated to B-physics and CP-violation measurements. To exploit its physics potential good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large read-out pitch and long strips will be used for the LHCb Inner Tracker behind the magnet and the Trigger Tracker station in front of the magnet. We report here about the design of the Silicon Tracker, test beam results and the electrical tests foreseen during production

Hyperon production in proton-nucleus collisions at a center-of-mass energy of sqrt(S_NN)=41.6 GeV at HERA-B and design of silicon microstrip detectors for tracking at LHCb

The topics of this thesis are the measurements of hyperon production in protonnucleus collisions at √ s = 41.6 GeV with the Hera-B detector located at DESY, Hamburg (Germany), and the design of silicon microstrip sensors for the LHCb experiment at CERN, Geneva (Switzerland). Λ, Ξ and Ω hyperons and their antiparticles were reconstructed from 113.5 · 106 inelastic collisions of protons with fixed carbon, titanium and tungsten targets. With these samples, antiparticle-to-particle ratios, cross sections integrated for the accessible kinematic region of Hera-B and single differential cross sections as function of transverse momentum, dσ/dpT (for Λ and Ξ) and rapidity, dσ/dy (for Λ only), have been been measured as well as the dependence of these quantities on the atomic number of the target nucleus, as parameterized using the Glauber model. The obtained ratios follow the same trend as found for the energy dependence of measurements from nucleus-nucleus collisions. Silicon microstrip sensors have been designed for the tracking system of the LHCb detector. Evaluating the performance in beam tests at CERN, the strip geometry and sensor thickness were varied optimizing for a large signal-to-noise ratio, a small number of read-out channels and a low occupancy. The detector is currently being built to be operational for first proton-proton collisions in autumn 2007.

The Silicon Tracker of the LHCb Experiment

LHCb is one of the experiments of the Large Hadron Collider at CERN, dedicated to B-physics and CP-violation measurements. To fully exploit the physics potential, a good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large read-out pitch and long strips will be used for the LHCb inner tracker after the magnet and the trigger tracker station in front of the magnet. We report here about the design of the silicon tracker, test beam results and the electrical tests foreseen during module production.