A filter implementation in a streaming data acquisition system at Grand RAIDEN in RCNP

Pair condensation caused by an effective attractive interaction is a common phenomenon in various fermion many-body systems. In the nucleonic system, neutron pair condensation is found via the measurement of neutron-pair transfer reaction while the existence of proton-neutron pair condensation is not confirmed yet. In order to quantify the p-n pair condensation, we plan to measure a pair transfer reaction of (⁴He,⁶Li) by using the Grand Riden magnetic spectrometer at RCNP.

In the (⁴He,⁶Li) reaction a lot of background events of ⁴He,³H, ²H and photon will be expected. Online filtering of such background events was performed by making trigger signals. But in our case trigger signals will be made by using a single thin plastic scintillator, which is sensitive to the background signals due to the large attenuation of scintillation light. Recently, a continuous readout data acquisition system has been developed among the collaboration in the SPADI Alliance. It has a capability of online filtering using non-standard detectors for a traditional trigger making, such as multi-wire drift chamber, VDC.

In this paper, an event filter using the VDC and its performance of the filter efficiency and the throughput as a function of data rate will be reported.