MSTD-16(Data sheet V1.0_01)

Frontend readout module
for standard
neutron detector tubes

MSTD-16 is a frontend module to read out up to 16 standard 3He or BF3 neutron
detector tubes. It can be remotely controlled and transmits time stamped amplitude data
to the data collector. The high peak rates of modern spectrometers require fast readout
electronics allowing to register data at the detector rate limit (about 100 kHz per tube)
with lowest possible dead time ratio.
Features:• Rate capability: 100 kHz per tube,
800 kHz continuous per MSTD-16 modulewith 16 detectors connected. Integrated
data buffer for high peak rates• Efficiency: very stable due to clearly
settable and stable amplitude thresholds• Time stamping at frontend:
100 ns resolution• Bias supply, filtered up to 3500 V.
Also well suited for BF3 filled tubes.
Preamp inputs withstand full discharges
of up to 2500 V.
• Detector interfacing:high voltage coax cables(MSDT-16 frontend connectors: SHV).
Cable lengths up to 3 m have only minor
effect on noise.
• Power consumption: 2.6 W at ±6 V,
allows operation in vacuum.
• Data bus: Lemo cable. Max 30 m length

mesytec GmbH & Co. KG
Wernher-von-Braun-Str. 1, D-85640 Putzbrunn, Germany
phone: +49 - 89 / 456007-30 fax: +49 - 89 / 456007-39
info@mesytec.com - www.mesytec.com

MSTD-16

Frontend readout module

Functional Overview
Rate capability, dead time

Readout path

The detector tubes are read out in groups ofsixteen which are connected to a single NIM
module MSTD-16. Each of the modules buffers
the amplitude and time stamp data of the 16
connected detector tubes and transmits them overa fast serial bus to a central NIM-module,
MCPD-8 (mesytec central processing device).
The event bus is physically a coax wire. TheMCPD-8 collects data of up to eight MSTD-16
modules, buffers the data and transmits it via
Ethernet to one (or more) data collecting PCs.
mesydaq software runs on Linux and handles theincoming data. Data is stored on harddisk anddisplayed live in histograms.
Transmitted event data

The MSTD-16 modules provide amplitude (with 9bit resolution) and time stamp (100 ns resolution)
data.
Remote control

For controlling the complete system, there is adata path back from the PC via Ethernet andeventbus. It is possible to configure gains,thresholds and pulsers from the PC, make pulser
testruns, and store the complete data set in aconfiguration file which is downloaded to theperipheral modules at the beginning of a new run.
Diagnostics

A built in test pulser, which feeds directly to thedetector inputs of the MSTD-16, easily allows tocheck all the signal path from preamplifier to thePC. The pulser, as all functions, can be remotecontrolled by software.
Time stamping

The MPSD-8 and MSTD-16 frontend modules use
their own time base (100 ns step) to label theincoming events in their buffer. When the events
are sent to the MCPD-8 via event bus, the timedelay from receiving the event at MSTD-16 input
to transmitting it to MCPD-8 via bus is added tothe event information. The receiving MCPD-8
adds this time offset to the event time stamp.

For a perfect readout electronics, the dead time ofthe system should only be determined by thedetector properties. The dead time is about 2.5 us
for thin detector tubes.
The MSTD-16 uses two very fast converters todigitize the amplitude of 16 detectors. This
converter adds almost no dead time because theanalog section can buffer the amplitudes of eachof the 16 detectors for up to three conversion
times.
An example for a TOF setup with fast detectors(2.5 us dead time): MSTD-16 is receiving anelastic bragg peak on one tube with 100 kHz, theother tubes will have a rate of 10 kHz.
So at the position of the bragg peak, at themoment the elastic neutrons hit the detector (someus) this detector will have a detector induced deadtime ratio of 25 % and 0.15 % converter deadtime. The other detectors of the same module atthe same time will have a detector dead time of
2.5 % and 0.15 % converter dead time.
After the elastic peak, the rate will usually decay
by orders of magnitude and the dead times will benegligible. No additional dead time is added
through all the processing chain down to the PC.
Input sensitivity (customer specific)

Can be varied by a factor of 4 by remote control
Standard range: 1.2*10-13 C (gain=1) ± factor of 2Dark rate @ UHV = 1200 V, no detectors
connected, 1 hour of warm up, sensitivity
1.2*10-13C. f < 1 count / hour per channel.

mesytec GmbH & Co. KG
Wernher-von-Braun-Str. 1, D-85640 Putzbrunn, Germany
phone: +49 - 89 / 456007-30 fax: +49 - 89 / 456007-39
info@mesytec.com - www.mesytec.com

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MSTD-16

Operation in vacuum

Frontend readout module

Mechanics

Outgasing, safe bias operation
The MSTD-16 can be safely operated undervacuum conditions from 10-1 mb to about 10-5 mb.
The upper limit (measured at 2.0 kV) is due to HV
discharge starting at this pressure. The lowerlimit is due to outgasing of PCB and cables.
The virtual leakage from PCB is about
5*10-4 mb*l/s after 24 hours of pumping.

MSTD-16 is available as standard NIM module orin a housing for stand alone operation (e.g.
mounted directly behind the detector bank).
In any case it comes in a 1/12 NIM size case(164 x 250 x 34 mm³ plus SHV connectorsof 20 mm).

Heating
The PCB temperature in a vessel with 25 °C is30 °C over most of the area and max. 40 °C at asingle position near the ADC. The measured
temperatures allow safe operation in vacuum
without special cooling.

Internal building blocks
Preamlifiers

The detector charge signals are amplified by low
noise charge sensitive preamplifiers. The preamp
gain can be adjusted via remote control tocompensate for Detector gain variations.
Pulse Shaping

The signals from the gain adjust stage are filteredby trapezoidal shapers with 1 us FWHM.
The signals runs through a baseline restorer andthen to the window discriminator. The digital
output of the discriminator is used to actively
restore the signal. This is essential at high rates toreduce drift of base line and keep a stabledetection threshold.
Then the signals of the tubes are digitized, and atime stamp is added.

MPSD-8+ in a stand alone box with fixture latches.
Mechanical properties are identical to MSTD-16.

mesytec GmbH & Co. KG
Wernher-von-Braun-Str. 1, D-85640 Putzbrunn, Germany
phone: +49 - 89 / 456007-30 fax: +49 - 89 / 456007-39
info@mesytec.com - www.mesytec.com

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