UCN
The Ultracold Neutron group, now the TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration was created to measure the neutron electric dipole moment (nEDM). This fundamental property, if non-zero, has serious ramifications for resolving the Baryogenesis problem.
Overview
The project has two main components: (a) the UCN source and (b) the nEDM experiment.
The source was largely completed and shown to be functional in 2026. It is operated primarily though EPICS, with monitoring though MIDAS histories with a MySQL database. It operates on beamline 1U (BL1U), splitting off of 1V (which later becomes BL1A). With a fast kicker magnet, the TUCAN collaboration can kick individual beam buckets to BL1U to take a fraction of beam, while enabling beam to BL1A. Design operating current is 40 uA. The UCN source has two end stations for experiments: one for the nEDM experiment, and the other is planned for PENeLOPE.
The nEDM experiment is the primary experiment for the UCN source and is composed of many subsystems, each with their own controls and DAQ setup. Experiments are generally conducted as follows:
- produce UCNs in the source,
- open a valve to let the UCNs diffuse to the experimental chamber
- store the UCNs in the chamber for some time, while applying high voltage, and RF pulses
- open the chamber valve to let the UCNs diffuse to the detectors
The subsystems with DAQ interfaces are as follows:
UCN Source
Produces UCN
Controlled through EPICS, monitored with MIDAS. Some MIDAS controls are implemented, such as the AutoStat page and the UCN sequencer.
Comagnetometer
An atomic gas (199Hg) inhabits the cell the UCNs are stored in. The gas is polarized with a free laser, and that polarization state is also measured with a laser. Measures magnetic field.
DAQ not yet implemented
Cs Magnetometers
An array of glass cells containing Cs gas are distributed inside the magnetically shielded room. The polarization state is also pumped and probed with lasers, this time through fibre optics. Measures magnetic field gradients.
DAQ exists as a set of student python scripts, yet to be integrated into MIDAS
B0 Coil
A coil which produces a highly stable and uniform static magnetic field
DAQ not yet implemented
B1 Coil
A coil which produces the oscillating RF fields for spin flips
DAQ not yet implemented
Shim Coils
An array of coils inside the MSR to homogenize the field
DAQ exists as a python script which controls an arduino, yet to be integrated into MIDAS
Guiding coils
An array of coils to maintain UCN polarization in their journey to and from the magnetically shielded room
DAQ not yet implemented
Ambient Magnetic Coil (AMC)
A large Helmholtz coil to counteract the cyclotron magnetic field
DAQ not yet implemented
High voltage
A large electric field to tease out the electric dipole moment
DAQ not yet implemented
Ambient monitoring
Monitoring of ambient temperature and magnetic field
Temperature
Measured through "canaries": battery-powered arduinos with a temperature sensor on the TRIUMF IOT network. Integrated into MIDAS. Frontend repo
Magnetic Fields
Measured through fluxgates and a custom DAQ produced by the TRIUMF electronics group. Frontend repo
Machines
The below list is incomplete, needs expanding
| Hostname (.triumf.ca) | Purpose | Location | OS | Status |
|---|---|---|---|---|
| daq01.ucn | Legacy primary DAQ machine and MIDAS host | UCN counting room | CentOS7 | Active |
| daq02.ucn | Runs digitizer frontend | Meson hall B2 | CentOS7 | Active |
| daq04.ucn | Multi-monitor EPICS control station | UCN counting room | Ubuntu 24 | Active |
| daq06.ucn | Test environment | Virtual machine | Ubuntu 24 | Active |
| daq07.ucn | Laser enclosure frontend | Laser enclosure, Meson hall B2 | Ubuntu 24 | Active |
| tucan01.ucn | New primary DAQ machine and MIDAS host | UCN counting room | Ubuntu 24 | In setup |
| ktm-readout.ucn | Kicker timing monitor frontend and web host | Cyclotron roof | Ubuntu 24 | Active, untested |
| ktmserver | Legacy KTM web host | Virtual machine | CentOS7 | Active |
DAQ Software and Setup
Directory Organization
Here we describe the organization and setup of the DAQ computer. While there are many other directories not listed here, they are outside of the core functionality of the main DAQ.
/home/ucn/(shared home)online/(daq01 midas main directory)autostat(python script to automate cryostate functions)epics2midas(read EPICS variables to midas ODB)fe_canary_env_temp(canary temperature monitor)fefluxgate(read custom orange DAQ box for fluxgates)ktm(Legacy KTM frontend)odb_dumps(Main repository of regular ODB dumps)scmfe(SCM frontend)sequence-control(UCN sequencer frontend)shift_schedule(Scheduler frontend)ucn-alarms-notification(Alarm actions: phone/email users)ucn_detector_analyzer(Main UCN counting: processing/online analysis - produce root files)ucn-v1725(CAEN digitizer frontend, runs on daq02.ucn)ucn-web-control(Custom pages)
packages/(source and build directories: MIDAS, EPICS, CAEN, ROOTANA, etc)
/data3/(large storage drive)ucn/midas_files(.mid.gz files and similar)ucn/root_files(.root, for analysis, after preprocessing)
Setup Instructions
Here's the general path to setting up the main DAQ machine (steps taken on tucan01.ucn):
- Set up ubuntu 24 as per the instructions here
Contacts
Some useful contact persons (TRIUMF PIs):
- R. Picker
- N. Yazdandoost