A noiseless kilohertz frame rate imaging detector based on microchannel plates read out with the Medipix2 CMOS pixel chip

Renz

J. Am. Soc. Mass Spectrom.

2011

Methods to visualize the two-dimensional (2D) distribution of molecules by mass spectrometric imaging evolve rapidly and yield novel applications in biology, medicine, and material surface sciences. Most mass spectrometric imagers acquire high mass resolution spectra spot-by-spot and thereby scan the object's surface. Thus, imaging is slow and image reconstruction remains cumbersome. Here we describe an imaging mass spectrometer that exploits the true imaging capabilities by ion optical means for the time of flight mass separation. The mass spectrometer is equipped with the ASIC Timepix chip as an array detector to acquire the position, mass, and intensity of ions that are imaged by matrix-assisted laser desorption/ionization (MALDI) directly from the target sample onto the detector. This imaging mass spectrometer has a spatial resolving power at the specimen of (84±35)μm with a mass resolution of 45 and locates atoms or organic compounds on a surface area up to~2 cm 2 . Extended laser spots of~5 mm 2 on structured specimens allows parallel imaging of selected masses. The digital imaging mass spectrometer proves high hit-multiplicity, straightforward image reconstruction, and potential for high-speed readout at 4 kHz or more. This device demonstrates a simple way of true image acquisition like a digital photographic camera. The technology may enable a fast analysis of biomolecular samples in near future.

Section: Discussionmentioning

confidence: 99%

“…The Timepix offers the capability of high event rates up to 4 kHz [21] and allows very fast data acquisition with an appropriate interface for data transfer. The experimental setup presented here was not optimized for fast data acquisition, since more advanced USB-based readout modules are currently being developed [22].…”

Section: Discussionmentioning

confidence: 99%

Digital Imaging Mass Spectrometry

Renz

J. Am. Soc. Mass Spectrom.

2011

Review of Scientific Instruments

“…The time over threshold output is directly proportional to the amount of charge deposited on the particular pixel, i.e., to the energy of the detected particle. This is an option that is very important when centroiding algorithms are applied to achieve subpixel spatial resolution for events that lead to a detectable signal over a range of pixels, such as the signals that can be detected when electron or ion signals are first amplified using a mcirochannel plate detector placed in front of the Timepix detector, 26,27 as will be further explained in a later paragraph.…”

Section: The Medipix/timepix Chipsmentioning

confidence: 99%

“…Depending on the distance and extraction voltage between the MCP and the Timepix ASIC, the charge cloud coming from the MCP will cover multiple pixels. Using the above-mentioned ability to determine the amount of charge deposited per pixel, a weighted centroiding algorithm can be used to achieve spatial resolution well below 10 m. 27 In this case the size of the MCP pores becomes the limiting factor. A similar technique has been known and applied also in VMI measurements for quite some time.…”

Section: High Position Resolution Measurementsmentioning

confidence: 99%

Velocity map imaging using an in-vacuum pixel detector

Gademann

Huismans

Gijsbertsen

et al. 2009

The use of a new type in-vacuum pixel detector in velocity map imaging (VMI) is introduced. The Medipix2 and Timepix semiconductor pixel detectors (256 x 256 square pixels, 55 x 55 microm2) are well suited for charged particle detection. They offer high resolution, low noise, and high quantum efficiency. The Medipix2 chip allows double energy discrimination by offering a low and a high energy threshold. The Timepix detector allows to record the incidence time of a particle with a temporal resolution of 10 ns and a dynamic range of 160 micros. Results of the first time application of the Medipix2 detector to VMI are presented, investigating the quantum efficiency as well as the possibility to operate at increased background pressure in the vacuum chamber.

“…The Medipix and Timepix [1] application specific integrated circuits (ASICs) are pixelated devices (256 × 256) where each pixel has an amplifier and discriminator network that can count individual charge pulses, and in the case of the Timepix, also measure the time of arrival or amplitude of the charge event. These ASICs can be used to readout imaging microchannel plates, whose output electron charge pulses represent information such as the spatial location and time of arrival of the stimulating input quanta (photons [2], electrons [3], neutrons [4] or ions [5]. The main advantages of these ASIC readouts of MCPs is their very low amplifier noise, (∼ 75 electrons rms), allowing for the operation of the MCP(s) at low gains (< 10000) thereby extending their lifetime at high input rates as well as high local rates.…”

mentioning

confidence: 99%

MCP detector read out with a bare quad Timepix at kilohertz frame rates

Vallerga

Raffanti²,

Tremsin

et al. 2011

J. Inst.

The existing Berkeley neutron sensitive MCP/Timepix hybrid detector has been very successful at demonstrating energy resolved spatial imaging with a single Timepix ASIC read out at a ∼ 30 Hz frame rate where each neutron's position and time (energy) is determined (X,Y,E). By increasing the detector format using a quad arrangement of Timepix readouts and increasing the frame rate to 1 kHz, we can increase our total event throughput by a factor of 120, thereby taking full advantage of the high fluxes of modern pulsed neutron sources (10 6 n cm −2 s −1 ). The key to this conversion is a new design for the ASIC readout, called the Berkeley Quad Timepix detector, consisting of 3 major subsystems. The first is a quad (2 × 2) bare Timepix ASIC board mounted directly behind the neutron sensitive MCPs in a hermetic vacuum enclosure with a sapphire window. The data from the Timepix ASICs flow to the second subsystem called the Interface board whose field programmable gate array (FPGA) rearranges and converts the digital bit stream to LVDS logic levels before sending downstream to the third subsystem, the Roach board. The Roach board is also FPGA based, and takes the data from all the ASICs and analyses the frames to extract information on the input events to pass on to the host PC. This paper describes in detail the hardware and firmware designs to accomplish this task.