The Cryogenic Apparatus for Precision Tests of Argon Interactions with Neutrino (CAPTAIN) program is designed to make measurements of scientific importance to long-baseline neutrino physics and physics topics that will be explored by large underground detectors. CAPTAIN began as part of a Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development (LDRD) project and has evolved into a multi-institutional collaboration. The program employs two detectors. The CAPTAIN detector is a liquid argon TPC deployed in a portable and evacuable cryostat that can hold a total of 7700 liters of liquid argon. Five tons of liquid argon are instrumented with a 2,000 channel liquid argon TPC and a photon detection system. The cryostat has ports that can hold optical windows for laser calibration and windows for the introduction of charged particle beams. Assembly of some detector components has begun while others are being acquired. The commissioning period will end in the summer of 2014. During commissioning, laser calibration and cosmic-ray data will be taken and analyzed.

Subsequent to the commissioning phase, the detector will be moved to a high-energy neutron beamline that is part of the Los Alamos Neutron Science Center. The neutron data will be used to measure cross-sections of spallation products that are backgrounds to measurements of neutrinos from a supernova burst and cross-sections of events that mimic the electron neutrino appearance signal in long-baseline neutrino physics.

The data will also be used to develop strategies for counting neutrons and evaluating their energies in a liquid argon TPC that are important for the total neutrino energy measurement in the analysis of long-baseline neutrinos.

The prototype detector is being fabricated in a cryostat supplied by the University of California at Los Angeles (UCLA) group and consists of a 1,000 channel liquid argon time-projection chamber (TPC). Assembly is underway and will be completed before the full CAPTAIN detector. The prototype detector will allow an end-to-end test of all components in time to make adjustments to the scheme employed by CAPTAIN. The prototype will collect cosmic-ray and laser calibration data earlier than will be possible in CAPTAIN allowing the development of analysis techniques at an earlier date. Finally, the prototype will allow for testing of calibration and other ideas in parallel to the running of CAPTAIN.

Subsequent to the neutron running, the CAPTAIN detector will be moved to a neutrino source. There are several possible neutrino sources of interest. The two most likely neutrino possibilities are an on-axis run in the NuMI (Neutrinos at the Main Injector) beamline at Fermi National Accelerator Laboratory (FNAL) and a run in the neutrino source produced by the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. An on-axis run at NUMI produces more than one million events of interest in a two or three year run at neutrino energies between 1 and 10 GeV. The neutrino studies are complementary to the MicroBooNE experiment, which will measure similar interactions at a lower, complementary energy range - 0.5 to 2 GeV. Many important exclusive and inclusive charged and neutral current channels will be measured by such a run.

The SNS produces a neutrino source as a byproduct of its neutron production. The neutrinos result from the decays stopped positively charged pions and muons. The neutrino energy spectrum produced from these decays is a broad spectrum up to 50 MeV. If located close to the spallation target, CAPTAIN can detect several thousand events per year in the same neutrino energy regime where neutrinos from a supernova burst are. Measurements at the SNS yield a first measurement of the cross-section of neutrinos on argon in this important energy regime. In addition, this would be the first measurement of low-energy neutrinos in a liquid argon TPC. This is critical for the interpretation of a supernova burst in the LBNE far detector and is crucial for the design of the LBNE light collection and DAQ systems.

A white paper prepared for the U.S. High Energy Physics Community Summer Study prepared by the CAPTAIN collaboration can be found here.