Educational Alibava System
The Educational Alibava System is a complete instrumentation system dedicated to Silicon Microstrip Radiation Detectors, representing the state-of-the-art in detector characterization.
It is based on the Alibava System largely used within the CERN community to test microstrip detectors for particle and nuclear physics experiments.
The system can be configured to work with laser light or radioactive sources.
The set-up is ideal for making basic or complex experiments with silicon microstrip detectors similar to the ones performed in the actual research field, in facilities like CERN (LHC), DESY, FERMILAB, Synchrotrons, etc.
This simple electronic equipment establishes the basis for an affordable and complete set of student laboratory experiments.
Find out what kind of experiments you can do with EASy with this summary.
Exercises brochure
EASY EXERCISE VIDEOS
CONTROL UNIT
The Control Unit controls the Sensor Unit that communicates with the PC software.
Xilinx device retained with support chipset
Plug and play.
Interface with Detector board via 34 IDC connector.
Incorporates all control, powering for Sensor Unit.
USB 2.0 interface.
HV module to supply the detector bias.
Dimensions: 169x52x120 mm3 (WxHxD)
The Mother Board is intended to process and digitize the analogue data that comes from the analogue readout chips. It also processes the trigger input signal of the diode in case of radioactive source setup or it generates an output trigger signal if a laser setup is used. Moreover, it controls the whole system and it communicates with the PC software via USB 2.0 interface, using an FPGA with an embedded processor and custom logic. The Mother Board also generates the power for the Sensor Unit.
SENSOR UNIT
The Sensor Unit accommodates one readout ASICs chip, providing 128 analogue input channels with a 40 MHz clocked analogue pipeline (maximum programmable latency of 4 μs).
The trigger signal is generated on the same Unit.
Dimension: 82x32x120 mm3 (WxHxD)
MICROSTRIP SILICON DETECTOR
P-on-N silicon microstrip, polysilicon biasing resistors, AC coupled.
128 channels with pitch 160 µm.
Thickness: 300 µm.
VFD < 60 V.
IL (@VFD) < 10 nA/strip.
Other thicknesses and pitch are available on demand.
LASER SOURCE
Laser diode 0.5 mW
Wavelength: 980 nm.
5 ns Pulses width.
Optical fiber output.
ACQUISITION SOFTWARE
A specific software controls the whole system and processes the data acquired by the detectors to store it in an adequate format. This format is compatible with the software used for further data analysis. With this software, the system can be configured and calibrated. Acquisitions with a laser setup or a radioactive source setup can be carried out as well to demonstrate and visualize the operating principles of the silicon strip detector. The system is Plug and Play and can be used with Windows, Linux, and macOS.
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EXPERIMENTS WITH EASy
This simple electronic equipment establishes the basis for an a fordable and complete set of student laboratory experiments, illustrating the operation of a silicon microstrip detector with LHC readout electronics. The students can be introduced from very simple concepts to more complex studies. Here we summarize some examples of suggested exercises.
1. Signal and noise
The students will be introduced to the concepts of pedestals, noise, cluster size, and signal to noise ratio
(SNR). This is an important aspect from the operational point of view to distinguish the genuine signals from the electronics noise. The system allows changing the SNR and the number of neighbor channels in the cluster formation.
The total noise of the system is measured as an equivalent noise charge (ENC) at the input of the amplifier. The student can measure the dependency of mean noise with the reverse voltage or with the temperature, learning their e ects in the total ENC through the sensor capacitance, leak current, etc. The system can be calibrated to obtain the noise in a unit of equivalent electrons.
2. Passage of particles through matter
The signal formation in the silicon sensor is due to the ionizing energy loss of the incident particles. One can study the charge deposition of a MIP using an Sr90 source. The system allows the reconstruction of the pulse shape by measuring the signal as a function of the time between the trigger signal and the periodic readout signal that takes place every 25 ns. The trigger signal is provided by a diode pleased below the microstrip detector. The parameter of the chip has been fixed to modulate the pulse shape and to obtain the maximum of the signal within the time window of the system
Figure 1: Charge deposition of a MIP (Sr90 source)
The analysis software allows defining the time interval where the signal has its maximum to calculate the charge deposition. Since the interactions between charged particles and the semiconductors are statistical in nature, the total energy deposited by each particle
will vary. However, the energy distribution produced over a large number of events is predictable and follows a Landau distribution [7] as shown in figure 1. From the previous distribution one can obtain the mean charge deposition and by fitting the Landau function the more probable charge deposition (MPC) of a MIP particle in ADC counts units. The system provides self-calibration to obtain the charge deposition in electrons.
3. Charge collection, depletion voltage, and electric field
The incident particle creates electron-hole pairs all along its pass through the sensor bulk. But only those pairs created in the depletion region contribute to the signal thanks to the electric field, which drifts them away. Therefore the signal depends on the size of the depletion region. The students will be introduced to the concept of Charge Collection Eciency (CCE) and its correlation with the depletion voltage. CCE could be evaluated using a 90 Sr source or an infrared laser ray. Using 90 Sr source for each reverse voltage one can obtain directly the charge collected (figure 2). Using an infrared laser, an arbitrary charge is injected, however, a posterior calibration could be applied; the advantage of using a laser source is the higher rate of the data acquisition.
Figure 2: Charge collection variation with the reverse voltage for a MIP (Sr 90 source) in a 300 m strip detector.
Figure 2 can be used to define the E ective DepletionVoltage (EDV) as the reverse voltage at which the CCE reaches 80% of the maximum Charge Collection value to be compared with the nominal depletion voltage provide with the sensor characterization (obtained by bulk
capacitance measurement).
4. Strip structure, charge sharing, and position resolution
The EASY system includes a 980 m pulsed laser with optical fiber output connected to micro-positioners to focus the laser and move the inject charge around the detector. The laser signal can be moved perpendicular to the strip direction to study to structure the strips (figure 3). Depending on the incidence point, the charge collected can be shared between adjacent strips. Students can investigate the e ect of charge sharing in the position resolution of microstrip detectors.
Conclusions
Figure 3: Charge collected in three adjacent strips when the laser is moved perpendicular to them. The laser light is reflected on the aluminum of the strips, while the charge is sharing between contiguous strips when laser light hits the inter strips zone. On the right, a sketch of the laser incidence and reflection on the strips.
EASY is the new version of the Alibava System, a compact and portable system for the characterization of silicon microstrip radiation detectors. Alibava System is adapted to be used in instrumentation lectures at the university teaching laboratories. The EASY system makes it more suitable for handling by undergraduate and postgraduate students. The system can be configured to work with laser light or radioactive sources. The set-up is ideal for making basic or complex experiments.
USER'S MANUAL AND EXERCISES BOOK
The kit incorporates the user manual and a specific exercises book ideal for introducing the student to the high-energy physics/particle physics experiments.
Download the list of the first set of exercises already developed.
Download and get to know the teacher's experience using EASy.
ACKNOWLEDGMENT
The research was partly supported by the Spanish National Program for Particle Physics (under Grant FPA2009-13234-C04 and FPA2012-39055-C02), the UK Science and Technology Facilities Council, and ALIBAVA SYSTEM, S.L. ALIVABA system is sold under license of the Spanish National Research Council (CSIC) and University of Valencia (Spain).
References
[1] R. Marco-Hernandez. A portable readout system for silicon microstrip sensors. Nuclear Inst. & Meth. A, Vol. 623, Issue 1, 1 November 2010, Pages 207-209.
[2] C. Da Vi et al.,3D active edge silicon sensors: Device processing, yield, and QA for the ATLAS-IBL production. Nuclear Inst. & Meth. A, Vol. 699, 21 January 2013, Pages 18-21.
[3] G. Casse, et al., Charge multiplication in irradiated segmented silicon detectors with special strip processing. Nuclear Inst. & Meth. A, Vol. 699, 21 January 2013, Pages 9-13.
[4] R. Bates, et al., Characterization of edgeless technologies for pixellated and strip silicon detectors with a micro-focused X-ray beam. Journal of Instrumentation, 2013, Vol. 8, Issue 01, Article P01018
[5] P. P. Allport, et al., Characterisation of micro-strip and pixel silicon detectors before and after hadron irradiation. Journal of instrumentation, 2012, Vol. 7, Issue 01, Article C01105
[6] G.F. Knoll. Radiation Detection and Measurement, volume 3rd Edition. John Wiley & Sons, 2000.
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