Ground Array
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MARIACHI Live
MARIACHI Scintillator Sites Live Display
A newer version of the MARIACHI Live display is here. This combines the live update with Google Map and is based on the newer data collection system. If you'd like, you can look at the same data in Google Earth by creating a link to http://www-mariachi.physics.sunysb.edu/data/status/status.kml
Eventually this display will replace both the MARIACHI Live and the MARIACHI Collection Sites displays.
MARIACHI Collection Sites
MARIACHI data is collected from sites located across Long Island.
Upgrade for new detectors/DAQ system status.
MARIACHI Scintillator Ground Array
The MARIACHI ground array will be used to detect extended showers and record the time of occurrence using a GPS clock. The shower detector is composed of 4 scintillators, each with 0.25m2 located at the corners of a high school classroom, with an additional identical counter mounted in one of the corners. The signals from the five detectors will be fed into a dedicated circuit board. This board has a Field Programmable Gate Array (FPGA) that will allow us to program any desired logic between the counters. In particular coincidence signals from the corner with the counter pair will provide a continuous monitor of the local cosmic ray rate. This pair can then be put in coincidence with each of the other three corner counters, with pairs of these counters, or with all the counters together. This will provide useful information on the performance of each of the counters, and on the variation of the cosmic ray rate at low to intermediate energies. The coincidence of all 5 counters defines a detection area specific to the detector separation. In the prototype, the scintillators were mounted at the top four corners of a room defining a detection area of 13.5 m2. This arrangement biases towards events with the large particle densities produced by a UHECR. The detection threshold estimated by simulations is approximately 0.1 EeV. Showers of this energy have footprints of approximately 1 km in radius and therefore each scintillator station is efficient for detecting UHECR of at least this energy over an area of 12-15 km2. Coincidences between several stations will provide evidence of even higher energy primaries. For simplicity of operation we will initially store only the time of occurrence for four-fold coincidences. The output of the coincidence circuit board will connect to a Spectrum Instruments GPS clock and frequency reference.
Shower detectors as developed in the prototyping phase will be used in conjunction with radio cosmic ray scatter (RCSC) detection to provide a confirmation signal for the radio signal. Ideally, the scintillator stations should cover as much area as the estimated radio coverage. One of the unique features of the MARIACHI approach is to involve high school teachers and students in the assembly and operation of the ground based array, integrating them directly into the scientific collaboration. This provides an opportunity for these students and teachers to become part of a forefront scientific experiment of vital importance, and provides to MARIACHI the critical confirmation of the technique. In later phases, MARIACHI could be scaled up by adding more RCRS and ground sites, and could also be integrated with existing and proposed ground arrays, such as Auger, for definitive calibration of the observed RCRS signals.
Scintillation Detectors
Initial Design
The very first design, Version 0, used scintillator paddles glued to basement special phototubes. These required high voltage supplies, typically 1.7 to 2.0 kV. To protect the scintillators they were mounted on wooden boxes with plexyglass covers. Pros of this design - low cost and visible. Cons - fragile, time consuming for assembly.
Version 1
As the project evolved, a second generation detector was designed, Version 1. These detectors were built during a summer workshop together with students. The scintillators are housed in plywood dark boxes. The scintillator is the same as previously used. Gluing was abandonned and a optical cookie was used to make the coupling to the PMT. Pressure between PMT and scintillator is kept by a spring. This design uses phototubes from ADIT. High voltage is also generated immediately before the phototube base. The detector is relatively easy to use but a bit cumbersome to be built.
We found a number of curious problems during the manufacture. The most interesting is how porous the plywood used is. In spite of the interior black paint significant ammount of light leak was observed. Aluminum patches were used to fix this problem. It was clear also that wood is not a very good material because it expands and contracts depending on humidity and temperature. Therefore another iteration was required.
Final Design
A detailed parts list used in the construction has been compiled by Bob Warasila.
Coincidence Detection
Version 1
The input impedance is 50 Ohms and thresholds can be adjusted to as low as 15 mV, although in a typical installation they are set to 50 mV.
Version 2
The new board is currently being built and assembled at Brookhaven and Stony Brook. It was designed by Dean Schamberger. The signal is first filtered by a discriminator who threshold can be adjustedMore info below. This board uses an FPGA chip to do the coincidence logic and count the number of "events" that trigger the logic. Improving over the first board, this version now has the flexibility to record more types of information. It records the singles rates on all counters and also coincidences between 2, 3, and 4 counters in the room in addition to coincidences between all 5 counters. Labview software is used to program the FPGA and read data through a USB port.
The board is housed in a box being designed for convenience and safety in the classroom. Inputs for signal cable from the 5 counters will be labeled on the front of the box and should correspond to individual detectors. The discriminator threshold on each channel should be calibrated to match the individual PMT)More info below. A 7.0 V power supply also resides in the box. The power supply is itself powered by an AC outlet. This supplies power to the PMT in all 5 counters through labeled outputs on the housing box. Each individual PMT performs at the desired efficiency at slightly different voltages. Therefore, a resistor is placed inside the housing box in series with each output channel to drop the voltage to the desired value. These resistors are calibrated to match individual PMT'sMore info below.
A newer version of the housing box is being designed. Among other improvements, the incoming 120 V AC power will be sealed off to prevent accidental contact.
Time Tagging
MM/DD/YYYY hh:mm:ss.sssssss UTC
Scintillator Calibration and Operation
Go here for background and instructions for calibrating and operating the scintillators.
Data Collection
Currently, data collection is done using Perl scripts on the site computer. We may convert parts of this to LabView in the future. Go here for more information about our prototype Labview data aquisition software.
