Bhaskar Mukherjee

A Distributed System for Radiation Monitoring at Linear Accelerators

This paper discusses a system for an on-line neutron fluence monitoring at linear accelerators. The system consists of a SRAM-based detector and a radiation-tolerant read-out system. The neutron fluence was measured in several locations of the accelerator. Monitoring of the radiation environment in an accelerator tunnel is necessary to assure reliable long-term operation of electronic systems placed in the tunnel. Monitoring of the chamber is especially important during the design stage of a linear accelerator. The new design of 20 GeV linear accelerator X-ray Free Electron Laser (X-FEL) is currently approved for construction at DESY Research Centre in Hamburg , . The presented paper is based on our research and experimental measurement carried out at 1.2 GeV superconducting electron linac driving the Vacuum UltraViolet Free Electron Laser (VUV-FEL). The application of a pair of TLD-700 and TLD-500 or superheated emulsion (bubble) dosimeters enables the supervision of neutron fluence in accelerators . This process requires continuous and arduous calibration of TLDs, therefore this method is not convenient. Moreover, it is impossible to monitor the radiation environment in real-time. The presented system fills the market niche of real-time neutron monitoring for high-energy accelerators. Neutron fluence and gamma dose measured in this way can be used for the detailed analysis of the VUV-FEL or X-FEL environments. Monitoring of the radioactive area in a linear accelerator tunnel could be helpful to the diagnosis and reduction of beam losses. We have conducted experiments with the distributed system dedicated to neutron flux measurement at the DESY Research Centre in Hamburg. The devices were exposed to a neutron field from an Americium-Beryllium (n,alpha) source 241AmBe. The systems were installed in two accelerators: Linac II and VUV-FEL

Radiation monitoring system for X-FEL

Radiation produced during the operation of linear accelerators poses a potential threat to electronic devices installed in the accelerator tunnel. Therefore, a distributed radiation monitoring system was installed at five various spots in the Free electron LASer in Hamburg (FLASH) tunnel. The presented system allows us to measure radiation produced during the operation of a linear accelerator driving FLASH in real time. The system is composed of two modules: radiation-sensitive sensors and a radiation-tolerant readout system constructed with the application of commercial-off-the-shelf (COTS) components. The neutron dosimeter was constructed using an innovative application of a static random access memory (SRAM), whereas a well-known radiation-sensitive RadFET was used for gamma quantification.

The radiation tolerant readout system for srambased neutron detector

Bremsstrahlung gamma radiation and photoneutrons are produced during the operation of high energy linear accelerators. The functionality of electronic devices that are placed inside accelerator tunnels can be jeopardized because of the negative influence of generated radiation. Therefore, a radiation monitoring system able to gauge neutron fluence and gamma dose in real time was constructed. Radiation-sensitive dosimeters cooperate with a readout system. The readout continuously measures both types of radiation and sends quantified data to a main computer. The system is also placed in the tunnel, hence it must be insensitive to radiation or able to tolerate induced malfunctions. A few different readout systems were designed. This work presents the application of different readouts designed using commercial of the shelf (COTS) components. The presented hardware was tested with americium-beryllium neutron source. Finally, the systems were irradiated in a linear accelerator tunnel to estimate their immunity and suitability for a long-term reliable operation in the radioactive field

Investigations of Irradiation Effects on Electronic Components to be used in VUV­FEL and X­FEL Facilities at DESY.

Electronic components during High Energy Physics experiments are exposed to high level of radiation. Radiation environment causes many problems to electronic devices. The goal of several experiments done at DESY (Deutsches Elektronen Synchrotron, Hamburg) was to investigate nature of irradiation effects, caused damages and possible techniques of mitigation. One of aspects of experiments is radiation measurements. The propositions of building radiation monitoring system, using different semiconductor components, are presented. Second aspect is radiation tolerance. Different electronic devices were tested: FPGA chips, CCD sensors, bubble dosimeters and LED diodes. Components were irradiated in TESLA Test Facility 2 tunnel and in laboratory using 241Am/Be neutron source. The results of experiments are included and discussed.

In Situ Measurement of Neutron and Gamma Radiation Exposures During Intercontinental Flights using Electronic Personal Dosimeters and Bubble Detectors

During a long range intercontinental commercial flight from Europe to Australia the neutron and photon dose equivalents have been evaluated using a pair of electronic pocket dosemeters ALOKA PDM-313 and ALOKA PDM-111, respectively. A temperature compensated superheated emulsion (bubble) detector and an aluminium oxide TL-Dosimeter were carried together for the purpose of in-flight calibration of the electronic dosemeters. We have evaluated the radiation doses during flights from various cities in the northern hemisphere to Sydney (Australia). The results were compared with the cosmic radiation exposure calculated using the EPCARD and CARI 6 flight dose computation codes developed by GSF (Germany) and FAA (USA), respectively. A simple method of aviation dose interpolation based on polynomial fitting has been proposed.

A Concept of Irradiation Experiments System

In modern high energy physics experiments the electronics modules for controlling and/or data acquisition are very often exposed to various ionising radiation fields. Its well known that it can cause many failures during work of such systems, even total break downs. In such case, the studies of radiation hardness of electronic devices should take place to avoid problems during the lifetime of the experiment. This article describes the idea of a universal modular system, which is under development at Warsaw Univeristy of Technology, to perform radiation experiments of various types of electronic devices. The concept and main advantages of the system are presented and discussed.

Readout System for Cost-Effective Radiation Monitoring System

Bremsstrahlung gamma radiation and photoneutrons are predominantly produced during the operation of high-energy electron linear accelerators. Therefore, generated radiation could cause radiation damage of electronic devices installed in the accelerator tunnel. A real-time radiation monitoring system RadMon has been designed to monitor both types of radiation at crucial spots inside a free electron laser FLASH. Several different versions of readout systems were designed and tested to choose the most suitable architecture for the cost-effective readout of the radiation monitoring system RadMon.

Status of LLRF system development for European XFEL

LLRF control system consists of a few basic subsystems with the basic aim to give good quality beam from the XFEL laser. Some of the se subsystems, which are described here are: transient detector, finite state machine, precise timing distribution network, EM field stabilization control loop, etc. The paper summarizes the latest developments of these systems done during the last year.