The Floating Strip Micromegas Detector by Jonathan Bortfeldt

Author:Jonathan Bortfeldt
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

A telescope, consisting of six cm standard Micromegas with 360 strips and two cm resistive strip Micromegas with two-dimensional strip readout, was used as accurate track reference. The telescope is an improved version of the system, discussed in Sect. 5.1. The detector strips pointed in -direction, perpendicular hit information was provided by the two additional strip layers of the resistive-strip detectors. All strips of the standard Micromegas were read out using the Gassiplex based system, discussed in Sect. 4.​1.​1. For the resistive strip detectors, APV25 based front-end electronics interfaced with the Scalable Readout System have been used.

Traversing pions were detected by two scintillator layers, consisting of three individual mm scintillators, read out with Hamamatsu R4124 photomultipliers (Hamamatsu Photonics K.K. 2010). The trigger signal for both readout electronic systems was derived from a coincident hit in both layers. A VME CAEN V775N time-to-digital converter recorded the timing of the six individual trigger scintillators, that provided an additional coarse position information in -direction.

Since both systems, and especially the Scalable Readout System, miss trigger signals, offline alignment of data streams was enabled by acquiring the global trigger number with each electronics separately: in the VME based Gassiplex system, a CAEN V775N time-to-digital converter was used to record the output of a custom 12 bit event counter, named Triggerbox, Sect. 4.​1.​3. A dedicated APV25 front-end board was used to record the attenuated logic signals with the Scalable Readout System. Since the Triggerbox output signals have a fixed delay with respect to the original trigger signal, this enabled furthermore the reduction of the 25 ns time jitter, encountered in the APV25 system, Sect. 4.​1.​2.

In order to avoid missed triggers as much as possible, the internal busy logic of the VME components, i.e. Gassiplex readout and TDCs, was used to generate a global busy signal (second to right block in Fig. 5.13).

The detectors were flushed with a premixed Ar:CO 93:7 vol% gas mixture with a flow of 2 ln/h. The gas pressure in the detectors was stabilized at mbar using the gas system, described in Sect. 4.​2. Due to the approximately 30 mbar overpressure in the detector system, the drift gap of the large floating strip Micromegas is considerably deformed, Sect. 5.2.4.

Discharges between the mesh and the anode strips were counted for the floating strip Micromegas and three reference detectors with a FPGA based logic scaler, developed by the author. The FPGA controlled scaler reliably counts NIM signals with up to 80 MHz rate and communicates with the DAQ computer over an RS232 interface.1 The high-voltage for the gas detectors was provided by several two-channel iseg SHQ 224M high voltage supplies (iseg Spezialelektronik GmbH 2012).

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.