Samuel Henry

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Samuel Henry

Detector Development Scientist

My work is focused on developing precision instrumentation for particle experiments. My past projects include the readout system for the CRESST dark matter experiment and a 12-channel SQUID magnetometer for a cryogenic neutron electric dipole moment experiment. In 2014 I started a programme at Oxford to develop a 3He magnetometer for the Muon g−2 experiment, which will probe for New Physics through a precision measurement of the muon anomalous magnetic dipole moment.

I am interested in developing applications of particle physics technology for use in other fields, and have worked on the application of SQUIDs to study geomagnetism and magnetic signals associated with groundwater movement, and the investigation of potential industrial applications in geophysical exploration.

See my home page for further information, and my blog for a readable account of my adventures in particle physics research and outreach.

I am a Physics Lecturer at Hertford College and I tutor mathematics for first year physics students. I am a senior demonstrator in the nuclear physics teaching laboratory and give lectures on the particle physics graduate lecture course. I have also given problem classes for the C4 Particle Physics Major Option, and I lectured the first year circuit theory course for three years.

The Muon g-2 Experiment and 3He Magnetometry

The measurement of the anomalous magnetic dipole moment of the muon is a powerful probe for New Physics. This is done by comparing the measured value to the theoretical prediction. The 3.6σ discrepancy between these two values, revealed by the Brookhaven g−2 experiment, will be tested by a 0.14ppm measurement by the new g−2 experiment at Fermilab.

The g−2 measurement requires the 1.45T magnetic field across the muon storage ring to be monitored to 70ppb precision. This is done using proton NMR sensors, which must each be calibrated against a standard probe with a spherical water reference sample. The systematic uncertainty on the water calibration probe was not so significant for the E821 Brookhaven experiment. However in the new Fermilab experiment, it is predicted to be the largest single uncertainty contributing to the magnetic field measurement. An improved characterisation of the probe will reduce this to 35ppb, but an improvement on this will require a new probe.

I have started a work programme in Oxford to develop a new standard calibration probe using a 3He gas sample, with negligible diamagnetic susceptibility, avoiding the temperature and sample shape dependence.

Neutron Electric Dipole Moment and SQUID Magnetometry

The neutron electric dipole moment is a powerful probe of New Physics beyond the standard model. A non-zero measurement of this parameter would help pin down the CP-violating processes required to explain the matter-antimatter asymmetry of the Universe, and an improved limit would allow us to select and constrain theoretical models. Such precision measurement experiments are recognised as essential to complement searches for new physics at the LHC.

I developed a SQUID magnetometry system, and associated hardware and software, to track the magnetic field in the neutron measurement cell to sub-picotesla precision and operate in the superfluid environment without interfering with other aspects of the experiment.

The technology I developed for a neutron EDM has potential further applications in many other areas of physics. I have carried out research using SQUIDs for geomagnetic studies, and investigated industrial applications for geophysical exploration.

In collaboration with the LSBB underground laboratory, I have carried out a series to field trips to take measurements using multiple SQUID magnetometers to monitor magnetic field fluctuations and search for a signal correlated with the groundwater flow rate. I also led a project to investigate whether SQUID sensors could lead to improvements in geophysical exploration using the magnetotelluric (MT) technique (supported by the STFC Follow on Fund and ISIS Innovation).

Dark Matter Detectors

As a graduate student, I worked on the development and assembly of the 66-channel SQUID readout for the CRESST dark matter search. After completing my D.Phil. in 2003, I worked at the Gran Sasso laboratory, running the experiment; taking the data used to set limits on WIMP dark matter and identify the alpha decay of 180W; and supervising the installation of the new SQUID system and other components. I briefly worked on the EDELWEISS dark matter search and on R&D towards the planned 1-tonne dark matter experiment, EURECA.