ALIBAVA SYSTEM CLASSIC
The Alibava System Classic is a portable readout system for scientific uses. This system uses a front-end readout chip, which was developed for the LHC experiments to read out microstrip detectors. The system is suitable to characterize the properties of irradiated and un-irradiated microstrip sensors. The system hardware has two main parts: a daughter board hosting the readout and a mother board. The first one contains two readout chips and has fan-ins and sensor support to interface the sensors. The last one is intended to process the analogue data that comes from the readout chips and from external trigger signals, to control the whole system and to communicate with a PC via USB.
There is provision for an external trigger input (a silicon trigger board is available) and a 'synchronised' trigger output for pulsing an external excitation source (e.g. laser system). The system can operate with different types and different sizes of microstrip detectors:
- n-type (holes read out).
- p-type (electrons read out).
- Up to 256 input channels.
Different flavours of detector boards are available to accommodate detectors of different sizes. The system is designed to work with a radioactive source setup and laser setup: useful for comparing results with the same detector.
- The system works with laser setup and a β source.
- Irradiated detectors can also be tested.
- There is a Linux and a Windows version for the software.
Data acquired with the system can be easily processed using ROOT framework: some macros already developed.
A schematic of the Alibava System Classic:
The spectrum of a signal from a beta source in a microstrip p-type detector.
STANDARD DAUGHTER BOARD
The detector board accommodates two ASIC chips to read detector signals, a temperature sensor placed close to the chips and the fewest additional components. A 5V supply level is sent from the mother board. This supply level is regulated by two LDO (Low Drop Out) linear regulators for obtaining the dc supply levels required by the readout chips (2.5 V) and the buffer stage (3.3 V). The detector high voltage power supply is supplied directly to the detector board. This supply level is decoupled prior to the detector.
For this system the ASIC chip analogue output onto one port is used. In this case the analogue front-end pulse signal is sampled into the pipeline with the frequency of the ASIC chip clock (40 MHz). The peak voltage of the front-end pulse signal is proportional to the collected charge at the detector channel, the peak time of this signal is about 25 ns (depending on the load capacitance among other parameters) and the remainder of the peak voltage after 25 ns is below 30% (i.e. the ratio between the signal voltage 25 ns after the peak and the peak voltage). Therefore, a 65–70 ns pulse length is considered in order to reconstruct the pulse. For reading out a particular position of the pipeline, a pulse of 25 ns (TRIGGER) is generated by the mother board.
This pulse is sampled with the falling edge of the readout chip clock (CLK). The analogue pipeline latency has been fixed to 128 clock cycles, so this TRIGGER pulse is generated 128 CLK cycles after a particular front-end signal point has been sampled and stored in the pipeline. For the laser setup the TRIGGER pulse is generated for each event (i.e. laser pulse) with a delay programmed by the user regarding the event occurrence. For the radioactive source setup, the TRIGGER pulse is generated with a fixed delay regarding the event occurrence (i.e. a particle crossing the detector) and a time stamp for each event is obtained with a TDC in the mother board. Therefore, just one sample of the analogue pipeline is required per event in both setups. The pulse shape can be reconstructed by acquiring enough number of events.
The main task of the system software is controlling the whole system and processing the data acquired from the sensors as well as storing this data with an adequate format in a PC for further processing.
The software has two levels. The low level software deals with the data exchange by USB with the motherboard and with the low level data processing. No driver design is required at this level since the manufacturer of the USB controller provides with a ready-to-use driver (Virtual Com Port Driver). The high level software implements the GUI for the communication between the user and the system, the data monitoring as well as the data output file generation.
The software has been designed initially for running in a Linux operating system. However, a Windows version of the software is envisaged as well. Both the low level software and the high level software have been implemented in the same package and they have been designed using C++. Some macros for the ROOT framework have been developed in order to process the data obtained with the software.
Standard Daughter Board (DB)
The Standard Daughter Board accommodates up to two readout ASICs chips, each providing 128 analogue input channels, with amplification and an analog pipeline (clocked with 40 MHz, has a maximum programmable latency of 4 µs). The semiconductor sensors are connected to the readout ASICs by micro wire-bonding (25 µm diameter) using interposed metal-on-glass "pitch adapters". Thus, the sensor strip geometry is matched to that of the input pads of the ASICs. The customer can choose between two versions of the detector board, equipped with one or two ASICs.
On request, multi-chip boards can be designed and provided to accommodate the need of reading out detectors with a larger number of channels. Also, DBs to accommodate detectors with different readout orientations (e.g. strips with orthogonal orientation, double sided detectors ...) can be designed to the customer geometry.
- Self trigger generated by the ASIC chip
- Custom design
- Pitch adapters available on request
- Different geometries of the sensors
- Double sided sensors
Custom Daughter Board
- Custom design of the Standard Daughter Board
- Pittch adapters available on request
- Different geometries of the sensor
- Double sided sensors
- Multi-chip board for larger number of channels
- Wire-bonding or high density connectors
Based on silicon diode sensors with an amplifier included.
- One or two diode coincidence triggers
- Includes coincidence logic and threshold adjustment
- Inputs: 5V and sensor bias (20-30V)
- Output: TTL Trigger pulse
- Compatible with Alibava MB input to start data acquisition
- Assembly matching with Alibava DB
- Custom design available on request
Metal-on-glass "pitch adapters" (PA) route the individual detector output channels (strips) to the amplifier's inputs. We can provide custom-designed PAs to match any required detector geometry.
- Pitch adapters 80 to 80 µm pitch (box of 10).
- Pitch adapters 80 to 50 µm pitch (box of 6).
- Custom pitch adapters
- 220V AC/5 V DC power supply for the ALIBAVA mother board.
- USB cable between PC and ALIBAVA mother board.
- 5 m flat cable for connection between the Alibava board and DB.
- AB aluminium case with connectors.
- DB aluminium case.
- Lemo HV connectors for biasing the detectors through the DB (filtered low noise input).
A Portable Readout System for Microstrip Silicon Sensors (ALIBAVA), IEEE Tran. Nuclear Science, Vol. 56, No. 3, June 2009 [DOI: 10.1109/TNS.2009.2017261]
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