MLZ is a cooperation between:> Technische Universität München> Helmholtz-Zentrum Geesthacht> Forschungszentrum Jülich
The main duties and responsibilities of the group comprise the following:
One of the main projects of the group was the construction of the 1 × 1 m2 detector for the Small Angle Neutron Scattering Instrument SANS-1. Similar to the detector of the D22 instrument at ILL it consists of a linear array of 128 individual Position Sensitive Detectors of 1m length and 8mm diameter filled with 15bar of Helium-3. Read out by the charge division method the device provides 8mm x 8mm position resolution and 1MH count rate capability. After commissioning during 2012 the detector was successfully brought into routine operation.
The detector group was actively participating in the “MILAND “-collaboration, a NMI3 Joint Research Activity within the 6th European Framework Programme. Derived from the detector concept developed within “MILAND”, we presently built a Helium-3 based fast high resolution Multi Wire Proportional Chamber (MWPC) with 25 cm x 25 cm active area. Using an individual cathode wire charge readout applying the Time-over-Threshold method and a proper algorithm for online position recognition the detector aims for 1mm x 1mm position resolution (FWHM) and a few hundred kHz count rate capability.
Within the “GSPC “-collaboration, a present NMI3 Joint Research Activity, we have built a Micro Strip Gas Detector (MSGC) based Gaseous Scintillation Proportional Counter (GSPC) with Anger Camera Readout provided by an array of seven individual Photo Multiplier Tubes (PMT). The application of this new technology could enable the design of neutron counting detectors that exhibit high count rate capability of up to 1 MHz, sub-mm spatial resolution and low gamma sensitivity on a par with gaseous detectors. First evaluation of a complete GSPC detector at FRM II is foreseen in early 2013.
Gaseous detectors with multi layers of solid Boron-10 converters are one potential alternative to Helium-3 based neutron detectors. Being actively involved in several international collaborations, at FRM II we experimentally study the performance of such devices and compare it to elaborate GEANT4 simulation calculations. Special interest is given to the study of macro-structured converters providing enhanced detection efficiency. In cooperation with the ESS detector group, we have started to build a demonstrator device providing 40cm x 40cm active area aiming at 5mm x 5mm position resolution.
The backbone of the FRM II data acquisition hardware for individual neutron detectors is built by a whole family of PCI/cPCI based DAQ-boards using the M-module ANSI standard. The boards can be custom-tailored to the requirements of the individual instrumental applications, e.g. diffraction, MIEZE, etc. with the performance ranging from simple counting mode, multi frame counting mode, Time-of-Flight measurement to Pulse height analysis. After almost 10 years since its first design, the hardware of the DAQ-family is presently under complete revision and will replace the electronics boards installed from mid of 2012.
The high resolution MWPC will be equipped with a readout electronics and data acquisition system for 256 × 256 individual channels which is derived from our activities in the MILAND project. Each cathode wire is connected to a transimpedance amplifier and a discriminator generating a Time-over-Threshold signal which is analyzed by the digital processing unit. It consists of 2×2 FPGA based Pre-Processing Modules and a Correlation Module implemented in a standard VME64x crate with custom backplane. X, Y coordinates and arrival time T are then delivered in list mode to the DAQ-PC.
Dr. Karl Zeitelhack
Phone: +49 (0)89 289-14703