Building Pulsers







This is a request for funds from the Nuclear Physics Laboratory, Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign.  The funds will be used to construct pulser boards and pulser drivers that will be used for the testing of the MULAN detectors. The work will be managed by the James Madison University Particle and Nuclear Undergraduate Physics Group under the direction of Dr. Giovanetti.




Progress toward the ultimate goal of a precision measurement of the positive muon lifetime places the summer of 2003 as the target for construction and testing of the MULAN detector. The present plan is to assemble all the elements at the Loomis Laboratory of Physics and complete a first round of tests before their scheduled use in the fall of 2003.  A critical component for the testing is the LED flasher system.  This proposal will outline the costs associated with the construction of this system.


The LED flasher system combines blue LED pulsers and driver.  An LED pulser consist of a printed circuit board that responds to electronic triggers by discharging a capacitor through a blue LED thereby creating a light flash. (The pulser is based on the system[i] used by KAMLAND[1]).  The driver modules distribute triggers and power to the pulsers as well as set the LED light intensity. The intensity of the LED flash is determined by the charging voltage. The charging voltage is set for each pulser with a potentiometer in the driver.  The LEDs will be fitted with small plastic caps that will position optical fibers to capture and deliver the light to the 360 photomultiplier tubes of the MULAN detector.


The system is designed initially to create a realistic pattern of detector signals that simulates the actual experiment.  This will allow for verification of the data channels in terms of wiring, power and recording. This will also be used to test the data acquisition control and recording capabilities. The system will initially provide one pulser for each detector. The design will be expandable to two boards for each detector so that system can be upgrade for double pulse studies should they be necessary. Studies during the summer and the results of the data collection run in the fall will determine if the LED system will be needed to monitor timing systematics.  For these studies the system must be able to inject an event of well-known time into the data stream by firing the positron detectors. These events would be used to verify that measured times are independent of the starting event, that is, signals that arrive close to the event gate start are handled identically to signals that arrive late in the event gate.


To summarize the LED system has been designed to:


The MULAN detectors, shown in Figure 1, are grouped and supported by mechanical structures called houses. Groups of five or six pairs are combined in a single house, penthouses (10) and hexhouses (20).  In total there are 170 scintillator (50+120) pairs (340 individual detectors).  Five hundred pulser will be produced because of the cost reductions gained when buying components.


The driver design is based on the system that generates the triggers. This system which is referred to as the Flight Simulator will send triggers to the drivers in groups of 16. The drivers will therefore control 16 LED flashers. Drivers will be rack mounted 2u high units with front panel connectors, test points and potentiometers. This layout is shown in figure 2.

Text Box: Figure 1 MULAN Positron Detectors












Text Box: Figure 2 Front Panel of Driver





Each driver unit will contain:


A summary of the number of items required is shown in Table 1.

Table 1:   Number of items


A detailed list of parts and part costs for the pulsers are shown in Table 2. The total cost is  about $10,000 for 500 boards. This amounts to a cost of about $20.00 per channel.


The driver costs are summarized in Table 3.  Details of the driver boxes are less well defined. There will be 25 boxes each with 16 outputs with a total capacity of 400.  The total cost will be about 20.00 per channel with a total cost of  $10,000.


The completion of the calibration system with 500 pulser boards and 400 driver channels is expected to be $20,000. 

Table 2 Pulser costs


Table 3 driver cost



[1] KamLAND is a new neutrino experiment that developed modular light flashers.

[i] Gerald Przybylski, Herbert Steiner, Fred Bieser, John Wolf, A Compact LED Light Source for KamLAND, Kamland Note: Calibration-011107, November 7, 2001.