A. Nomerotski

The DELPHI silicon strip microvertex detector with double sided readout

The silicon strip microvertex detector of the DELPHI experiment at the CERN LEP collider has been recently upgraded from two coordinates (RΦ only) to three coordinates reconstruction (RΦ and z). The new Microvertex detector consists of 125 952 readout channels, and uses novel techniques to obtain the third coordinate. These include the use of AC coupled double sided silicon detectors with strips orthogonal to each other on opposite sides of the detector wafer. The routing of signals from the z strips to the end of the detector modules is done with a second metal layer on the detector surface, thus keeping the material in the sensitive area to a minimum. Pairs of wafers are daisy chained, with the wafers within each pair flipped with respect to each other in order to minimize the load capacitance on the readout amplifiers. The design of the detector and its various components are described. Results on the performance of the new detector are presented, with special emphasis on alignment, intrinsic precision and impact parameter resolution. The new detector has been taking data since spring of 1994, performing up to design specifications.

PImMS, a fast event-triggered monolithic pixel detector with storage of multiple timestamps

PImMS, or Pixel Imaging Mass Spectrometry, is a novel high-speed monolithic CMOS imaging sensor tailored to mass spectrometry requirements, also suitable for other dark-field applications. In its application to time-of-flight mass spectrometry, the sensor permits ion arrival time distributions to be combined with 2D imaging, providing additional information about the initial position or velocity of ions under study. PImMS1, the first generation sensor in this family, comprises an array of 72 by 72 pixels on a 70 μm by 70 μm pitch. Pixels independently record digital timestamps when events occur over an adjustable threshold. Each pixel contains 4 memories to record timestamps at a resolution of 25 ns. The sensor was designed and manufactured in the INMAPS 0.18 μm process. This allows the inclusion of significant amounts of circuitry (over 600 transistors) within each pixel while maintaining good detection efficiency. We present an overview of the pixel and sensor architecture, explain its functioning and present test results, ranging from characterisation of the analogue front end of the pixel, to verification of its digital functions, to some first images captured on mass spectrometers. We conclude with an overview of the upcoming second generation of PImMS sensors.

The LCFIVertex package: vertexing, flavour tagging and vertex charge reconstruction with an ILC vertex detector

The precision measurements envisaged at the International Linear Collider (ILC) depend on excellent instrumentation and reconstruction software. The correct identification of heavy flavour jets, placing unprecedented requirements on the quality of the vertex detector, will be central for the ILC programme. This paper describes the LCFIVertex software, which provides tools for vertex finding and for identification of the flavour and charge of the leading hadron in heavy flavour jets. These tools are essential for the ongoing optimisation of the vertex detector design for linear colliders such as the ILC. The paper describes the algorithms implemented in the LCFIVertex package as well as the scope of the code and its performance for a typical vertex detector design.

The application of the fast, multi-hit, pixel imaging mass spectrometry sensor to spatial imaging mass spectrometry

Imaging mass spectrometry is a powerful technique that allows chemical information to be correlated to a spatial coordinate on a sample. By using stigmatic ion microscopy, in conjunction with fast cameras, multiple ion masses can be imaged within a single experimental cycle. This means that fewer laser shots and acquisition cycles are required to obtain a full data set, and samples suffer less degradation as overall collection time is reduced. We present the first spatial imaging mass spectrometry results obtained with a new time-stamping detector, named the pixel imaging mass spectrometry (PImMS) sensor. The sensor is capable of storing multiple time stamps in each pixel for each time-of-flight cycle, which gives it multi-mass imaging capabilities within each pixel. A standard velocity-map ion imaging apparatus was modified to allow for microscope mode spatial imaging of a large sample area (approximately 5 × 5 mm(2)). A variety of samples were imaged using PImMS and a conventional camera to determine the specifications and possible applications of the spectrometer and the PImMS camera.

The timepix telescope for high performance particle tracking

The Timepix particle tracking telescope has been developed as part of the LHCb VELO Upgrade project, supported by the Medipix Collaboration and the AIDA framework. It is a primary piece of infrastructure for the VELO Upgrade project and is being used for the development of new sensors and front end technologies for several upcoming LHC trackers and vertexing systems. The telescope is designed around the dual capability of the Timepix ASICs to provide information about either the deposited charge or the timing information from tracks traversing the 14×14 mm matrix of View the MathML source pixels. The rate of reconstructed tracks available is optimised by taking advantage of the shutter driver readout architecture of the Timepix chip, operated with existing readout systems. Results of tests conducted in the SPS North Area beam facility at CERN show that the telescope typically provides reconstructed track rates during the beam spills of between 3.5 and 7.5 kHz, depending on beam conditions. The tracks are time stamped with 1 ns resolution with an efficiency of above 98% and provide a pointing resolution at the centre of the telescope of View the MathML source. By dropping the time stamping requirement the rate can be increased to View the MathML source, at the expense of a small increase in background. The telescope infrastructure provides CO2 cooling and a flexible mechanical interface to the device under test, and has been used for a wide range of measurements during the 2011–2012 data taking campaigns.

Pixel Imaging Mass Spectrometry with fast and intelligent Pixel detectors

We report on `proof of concept experiments in Pixel Imaging Mass Spectrometry (PImMS) using an ultra-fast frame-transfer CCD camera and also describe an intelligent CMOS sensor which is being developed for this application by the PImMS collaboration in the UK. PImMS is a combination of traditional TOF mass spectrometry and ion imaging. Information provided by the ion imaging gives access to valuable structural information of the molecule under investigation, in addition to the normal mass spectrum. Recording of the 2D spatial information of the arriving ions allows to reconstruct the ion velocity distributions for separate ion masses and to correlate them to each other. The new PImMS sensor will be capable of time stamping up to four arriving ions per pixel during the 200 μsec acquisition cycle with 100 nsec resolution which should meet the demanding requirements of complete recording of mass spectra of complex organic molecules.

Application of fast sensors to microscope mode spatial imaging mass spectrometry

The application of fast detectors to microscope mode spatial imaging mass spectrometry, in which the two-dimensional distributions of particular ion masses over a sample are projected onto a two-dimensional detector, allows the imaging of all mass peaks desorbed from a sample on each time-of-flight cycle. Detecting all fragments per duty cycle means that fewer ionisation and acquisition cycles are required for a full set of data, leading to a reduction in overall detection time, amount of sample required, and sample degradation. Results from a proof-of-concept experiment, in which a fast frame transfer charge-coupled device camera (CCD) with 10 ns time resolution was coupled to a modified velocity-mapped imaging apparatus, are presented.

PImMS: A self-triggered, 25ns resolution monolithic CMOS sensor for Time-of-Flight and Imaging Mass Spectrometry

In this paper, we present the Pixel Imaging Mass Spectrometry (PImMS) sensor, a pixelated Time-of-Flight (TOF) sensor for use in mass spectrometry. The device detects any event which produces a signal above a programmable threshold with a timing resolution of 25ns. Both analogue and digital readout modes are available and all pixels can be individually trimmed to improve noise performance. The pixels themselves contain analogue signal conditioning circuitry as well as complex logic totalling more than 600 transistors. This large number can be achieved without any loss of quantum efficiency thanks to the use of the patented Isolated N-well Monolithic Active Pixels (INMAPS) process. In this paper, we examine the design of the PImMS 1.0 device and its successor PImMS 2.0, a significantly enlarged sensor with several added features. We will also present some initial results from mass spectrometry experiments performed with PImMS 1.0.

First radiation hardness results of the TeraPixel Active Calorimeter (TPAC) sensor

The TeraPixel Active Calorimeter (TPAC) sensor is a novel Monolithic Active Pixel Sensors (MAPS) device developed for use as the active layers of a large area, digital electromagnetic calorimeter (DECAL) at a future e+e− collider. Further applications, which include the tracking and vertex systems for future lepton colliders and LHC upgrades have been proposed and it is therefore essential to characterise the behaviour of the sensor for these applications. We present the first studies of radiation hardness testing of the TPAC sensor. The performance of the sensor has been evaluated after exposures up to 5 Mrad of 50 keV x-rays. Under realistic ILC operating conditions a maximum decrease in the signal to noise ratio of 8% (15%) was observed after 200 krad (5 Mrad) which is already sufficient for proposed applications in future e+e− colliders.

Beam test results of FORTIS, a 4T MAPS sensor with a signal-to-noise ratio exceeding 100

We have tested the first 4T Monolithic Active Pixel Sensor (MAPS) for particle physics, FORTIS in a beam test. We have measured a signal-to-noise ratio of more than 100 for MIPs due to the excellent noise performance of the 4T architecture. Two versions of the sensor were tested; with and without deep P-well areas in-pixel. The deep P-well areas allow the incorporation of PMOS transistors inside the pixels without signal charge loss. The measured position resolutions were around 2 μm.