SenSyr News

The Syracuse University Experimental High Energy Physics Group and SenSyr developed the HPD Array Magnetic Calibration System for the CERN LHCb experiment. For more background see our previous article, SenSyr at CERN. The system has been installed at CERN and is now being tested. See “First Report on Full System” for initial performance.

LED bar being installed

LED Calibration Array in front of HPDs

Calibration System getting installed

The Syracuse University Experimental High Energy Physics Group and SenSyr developed the HPD Array Magnetic Calibration System for the CERN LHCb experiment. Each LED bar has 2590 LEDs driven by 19 daisy-chained boards. The light from each LED passes though a stacked collimator before leaving the bar to impinge on the HPD array. The HPDs (Hybrid Photo Diodes) operate sort of like a CRT television tube in reverse. The HPDs operate in the presence of a huge magnetic field as part of the LHCb experiment. The electrons moving within the HPD are affected by the ambient magnetic field and don’t land where they would without the field. The LED calibration system allows the HPD detector array to compensate for the complicated magnetic field interaction. A controller board allows a single ethernet connection to control the LED bar and the stepper motor subsystems.

Close-up of two controllers used in the HPD array calibration for the LHCb experiment at CERN. The controller allows ethernet-based communication with the LED calibration array and the motor control. We used a Lantronix XPORT module to handle the ethernet connection.

Two controller boards (one mounted to its power supply) used in the HPD array calibration for the LHCb experiment at CERN.

Close up of two controllers and a transition board used in the HPD array calibration for the LHCb experiment at CERN. The transition board regulates power at the LED light bar, as that is located on the end of a 50-foot cable. Control signals are transmitted through the cable from the controller as LVDS pair and converted back into single-ended signal lines at the transition board.

Videos of the LED calibration system on the test bench. The light bar is the black bar. The collimator side of the bar is shown. The collimators are machined from black-colored Delrin.