UCNB Simulations

The UCNB experiment is designed to measure the neutron decay correlation parameter 'B', the angle between the spin of the decaying neutron and the direction of the emitted neutrino. The experiment is carried out with 'ultra-cold' neutrons (UCN), those with low enough energy to be trapped in the experimental apparatus, greatly increasing the observation time. The angle is inferred from measurements detecting both the electron and proton decay products.

Data has been taken on the spectra of energy deposited in detectors on opposite ends of our 4.5m long tubular magnet/vacuum chamber. However, to benchmark our data and attempt to further understand systematic losses associated with the transport of particles through the material of our detectors (bremsstrahlung losses), particles hitting one detector and scattering back through the length of the volume (backscattering), and energy deposits in our detectors below the resolution of our detector (sub-threshold events). As such, we need to simulate a large quantity of UCN decay events (1-2M) for a broad collection of geometries, including modified electric fields in our vacuum chamber, as well as similarly sized simulations of the emission spectra of a variety of radioactive sources used in the calibration of the detectors.

The simulation runs using CERN's ROOT and GEANT4 packages, C++ object oriented physics simulation frameworks. The GEANT4 simulation package models the transport of subatomic particles through a user-defined geometry (consisting of both physical volumes as well as electric and magnetic fields). The simulation output is tabulated in the hierarchical data structure of a ROOT 'tree'.

We need to use the GEANT4 legacy version 9.2 (2010), as it is the last version of GEANT4 that includes the “G4hLowEnergyIonisation”. This is because UCNB simulations transport the proton with a maximum energy of around 700 eV through our detectors, which requires ionization at this energy. We also use the older ROOT version 5.34, the last production version version 6.0 which switched from Cint to the 'cling' C++ interpreter.

Participants

Lead PI: Christopher Crawford
Postdoc: Jon Wexler (external collaborator from NCSU)
Grad student: Aaron Sprow
Wenjiang Fan, Postdoc - External collaborator UV with VPN
Mark McCrea, Postdoc

David Perryman - External 

James David Bowman - (External, ORNL - 1 year access)

Leah Broussard, (External, ORNL - 1 year access, Added 07/10/2017)

Postdoc: Michael Kline

David Matthews, Graduate, 01/15/2020

Lars Hebenstiel, WKU Student working 2021Summer, Added 07/15/2021

David C Bowles, LCC cluster, Added 09/30/2021

Brandon D Stone, Added 11/24/2021 on LCC

Andrew Mullins, Chemical and Materials Engineering, LCC cluster, External, NIST Added 01/28/2022 

Himal Acharya, Post Doc, Added 03/14/2022 on LCC cluster

Shmad H Saftah, Added 04/06/2022 on LCC cluster

Francisco (Frank) M Gonzalez, Added 04/14/2022 on LCC cluster, External, ORNL

Design Calculation of Precision Surface Current Electromagnets

This project involves the application of a new technique to calculate the windings of precision electromagnetic coils based on the exact field requirements. It is based on a new interpretation of the magnetic scalar potential as a 'source potential' via Ampère's law. We solve a boundary value problem involving Laplace's equation, given the required fields a flux boundary conditions. The coil winding geometry is extracted from equally spaced contours of the output solution of the scalar potential.

Our group is designing spin transport magnetics to guide the polarized neutrons and Helium-3 atoms into the measurement cell of the nEDM experiment, an experiment being designed to measure the electric dipole of the neutron. This observable, which has already been constrained to < 3e-26 e*cm, has profound consequences on the matter dominance and relative absence of anti-mater in our universe. It is also sensitive to clear signatures of physics beyond the standard model.

This project will use the COMSOL simulation software to solve the classical Laplace equation on extremely fine meshes generated on CAD-produced models of active magnetic coil formers in the experimental apparatus. The large memory and matrix inversion capabilities of the dlx cluster will allow us to calculate the coil geometries accurately enough for the high-precision requirements of this experiment. This is an ongoing project to calculate the windings, construct and map different pieces of the complete apparatus.

Participants

PI: Christopher Crawford
Grad Student: Ali Frotanpour

Jason A Fry, External collaborator, Virginia University
Undergraduates:
Hunter Blanton
Patrick Montgomery
Benjamin Riley
Andrew Mullins
Matt Mousley
Jianxiao Wu
Jonathan Wexler
Wenjiang Fan, Postdoc - External collaborator UV with VPN

Wanchun Wei, External collaborator - Caltech
Mark McCrea, Postdoc

Tom Shelton

Gabija Ziemyte

Diana Sahibnazarovs

Bret Crawford, External, Gettysburg Added 12/03/2020

Publications:

1. “A Lightweight Method for Real-Time Waveform Fitting with Background Noise Rejection”, A. P. Jezghani, and L. J. Broussard, C. B. Crawford, IEEE Transactions in Nuclear Physics, 2019. (pending)
2. L. Broussard {\it et al.}, ``Detection System for Neutron $\beta$ Decay Correlations in the UCNB and Nab experiments'', %L. J. Broussard, B. A. Zeck, E. R. Adamek, S. Baeßler, N. Birge, M. Blatnik, J. D. Bowman, A. E. Brandt, M. Brown, J. Burkhart, N. B. Callahan, S. M. Clayton, C. Crawford, C. Cude-Woods, S. Currie, E. B. Dees, X. Ding, N. Fomin, E. Frlez, J. Fry, F. E. Gray, S. Hasan, K. P. Hickerson, J. Hoagland, A. T. Holley, T. M. Ito, A. Klein, H. Li, C.-Y. Liu, M. F. Makela, P. L. McGaughey, J. Mirabal-Martinez, C. L. Morris, J. D. Ortiz, R. W. Pattie Jr., S. I. Penttilä, B. Plaster, D. Počanić, J. C. Ramsey, A. Salas-Bacci, D. J. Salvat, A. Saunders, S. J. Seestrom, S. K. L. Sjue, A. P. Sprow, Z. Tang, R. B. Vogelaar, B. Vorndick, Z. Wang, W. Wei, J. Wexler, W. S. Wilburn, T. L. Womack, A. R. Young. \href{http://dx.doi.org/10.1016/j.nima.2016.12.030}{Nucl. Instr. Meth. {\bf A849}, 83 (2017)}, \href{http://arXiv.org/pdf/1607.02656.pdf}{arXiv:1607.02656} [physics.ins-det].

Grants:

1. We received a subcontract through ORNL from DOE for $405,366 for work related to the Nab experiment (we use the GPU farm for analysis).
2. We also have DOE contact DE-SC0014622 for $1,809,463 supporting Nab, and nEDM, (we use the GPUs for analysis)
3. Undergraduate Thomas Shelton received a DOE SULI internship at ORNL based on his research experience with LCC.