  A new fast neutron spectrometer named n-TPC has been designed by LPRI (Key
Laboratory of Particle & Radiation Imaging, Ministry of Education) at Tsinghua
University. The neutron energy spectrum can be calculated from the recoil angle
and energy of the recoil proton detected by a 704-pad GEM-TPC. In beam tests at
IHIP (Institute of Heavy Ion Physics, Peking University) in 2014, n-TPC
performed better than 6 percents at 6MeV energy resolution and 0.5 percents
detection efficiency. To find the best working parameters (the component and
proportion of the gas, the high voltage between each GEM layer, etc.) of the
n-TPC and support its application in various conditions, a multichannel
distributed DAQ has been design to read out the signals from the 704 channels.
With over 25 Ms/s sampling rate and 12 bit resolution for each channel, it can
record the time and amplitude information as well as traditional DAQs in the
TPC application domain. The main design objective of this distributed DAQ,
however, is more flexible parameter modulation and operation. It can support
the n-TPC without the limitation of the chassis and categorize signals arriving
from the 704 channels at the same time by different events without event
triggers.
