1 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov ABSTRACT In this note the design and integration of the LED monitoring system for LHCb hadron calorimeter is presented. It contains the simulation and experimental results obtained on the test beam with the first samples and prototypes of the electronics boards. The note is based on the result of several presentation and discussion on the LHCb CALO meetings and already published information. LED driver optimization and status of the LED triggering signal distribution board Design of LED monitoring system for HCAL Rustem Dzhelyadin, Anatoli Konoplyannikov, Vitali Matveev, Mikhail Soldatov, Valentina Yakimchuk 2 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov Table of Contents Introduction HCAL LED monitoring system. System overview Optical part LED driver and a PIN diode monitoring chain Design of the control voltage distribution subsystem Integration of the LED monitoring system on the HCAL detector. Placement of the electronic boards and connection with ECS References 3 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov A light emission diode (LED) monitoring system has been designed together with the HCAL module to allow exhaustive check and monitoring of the photo- tube (PMT) performance. Each of 52 modules contains two independently driven LEDs with light distributing clear fibers to 16 or 40 PMT reside at the back of the module. The main aim of the LED monitoring system is to monitor the PMT gain in time of data taking. Other important role of the system will be in time of the detector commission and testing in the LHC machine stops. The electronics of the LED monitoring system consists of three functional parts: Subsystem for a LED intensity control and distribution, Subsystem for a LED trigger pulse control and distribution LED drivers with LV power distribution The architecture of the subsystems is chosen taking into account following considerations: The DAC ICs should be kept in a region with a lowest level of radiation. The easy access for board exchange should be foreseen. A cable length should be minimized in order to avoid a ground loop voltage shift. 4 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov Optical part Each HCAL module is equipped with two light emission diodes. In normal operational conditions a light intensity for each diode will be set in ratio of about 1:4, due to the PMT gain along the module will be set in correspondence of a particle momentum. A light from the diodes are distributed to each photomultiplier by a clear fiber with diameter 1.2 mm type BCF-98 produced by Bicron. Photo of the optical fibres placement into HCAL module. Sketch of the optical part of the LED monitoring system placed into each HCAL module. 5 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov LED driver optimization The dedicated HCAL versions of the LED driver and PIN diode amplifier were redesigned taken in consideration the following reasons: 1) adaptation of the trigger signal level with the output signals of the LED trigger signal distribution board; 2) minimization of the LED driver power consumption; 3) unification of the electronic components with others calorimeter sub- detectors. The main LED driver features are: controlled light intensity DC isolation of the triggering signals for decreasing the ground loop noise edge sensitive triggering overshot circuit allows to decrease the trailing edge of a light flash dimension of the printed board is 40*70 mm*mm mechanical design is optimized for HCAL 6 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov Different types of light emission diodes (LED) were studied. At the moment the blue fast LED the WUSTLICH WU type tested by PS/SPD group is main candidate for using in the HCAL LED monitoring system. Other candidate is Bleu HL diode produced by the Everlight company has a good performance, but much expensive. Characteristics of the diodes are shown in Table 1. CouleurI lum (mcd)V fIf nom (mA) Angle vision l (nm) Wustlich WU Bleu HL V Table 1. Blue HL LED characteristics. LED choice 7 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov The pulse response comparison for two types of LED driving ICs( DS0026 and EL7212) with the fast orange LED. Driver IC choice Two type of the fast ICs for LED drive were studied: 1.DS0026 produced by National Semiconductors, 2.EL7212 produced by Intersil. DS0026 EL7212 8 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov Conclusion 1. The LED driver based on the fast EL7212 integrated circuit is about two times faster than DS0026 one and preferable for the HCAL application. Driver IC choice 9 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov As well known the optimal LED color for PM monitoring is green (520 nm), but a fast and not expensive green LED unfortunately not found. The pulse response comparison for two types of LED ( orange and blue WUSTLICH WU ). The measurements were done with LED driver based on EL7212 IC. LED choice orange blue 10 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov The pulse response comparison for non clipped and clipped signals. The measurements were done with LED driver based on EL7212 IC and blue WUSTLICH WU LED choice blue LED clipped not clipped 11 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov Conclusion 2. The blue LED WUSTLICH WU type using with the fast EL7212 IC is faster than required and could be used for the HCAL application, but an additional shaping circuitry is needed to match LED signal with the HCAL beam signal shape. LED choice 12 Overview of the HCAL LED monitoring PRR note CALO meeting Anatoli Konoplyannikov LED driver circuit optimization In previous designs the LED intensity control signal is applied to a power supply pin of a driver IC (Fig.1). In this case it was found that there is a big output signal delay variation as function of the LED intensity control voltage. The ten times amplitude variation leads at up to 10 nsec a signal delay. The circuit modification has been done. The driver IC power was fixed and a signal delay variation was decreased up to less than 1.5 nsec (Fig.2). Uctr Vcc OA EL7212 LED Trigger Uctr Vcc OA EL7212 LED Trigger +12 V 10 ns