NAPALI RAYMUNDO

1. Research Assistant
2. Engineer Intern
3. EE Consultant
4. Robotics Teacher
5. Wood
6. Clay
7. Electronics Etc.


About
Resume

P001 : Undergraduate Research Assistant

Particle Physics, Python, C, Shell, Cryostats, Statistics

My senior thesis and undergraduate research at Brown University was done in Gaitskell Lab, as part of the LZ Collaboration, a direct-detection dark matter search experiment located in Lead, SD. See P001.3 below for a more detailed explanation of the experiment.



P001.1 My Project
My project sought to optimize the control circuitry of the R11410 Photo-Multiplier Tube for the requirements of the LZ collaboration. I did so by modifying the PMT-mounted PCB to have control over field shape. Runs were then conducted evaluating the relevant device parameters (collection efficiency, gain, dark rate, linearity) at different field configurations. Please read my paper linked at right for more info and results.

Experimentally, runs were taken in a light tight cryostat just above LN2 temperatures with N2 backfilled to atmospheric pressure. Test photons were delivered using two pulsed LED’s and a fiber-optic bulkhead. Crucial single-photon light levels were reached with a combination of pulse tuning and statistical methods.

Test equipment, experimental methods, cryostat operation, as well as control and analysis software were all developed and performed by me.
Thesis download



P001.2 Project Gallery

PATRIC (PMT Array Test Rig in Cryogens)
Hamamatsu R11410 PMT
Optical bulkhead for single photon pulsing
Control equipment bench setup
Single event pulse trace examples

P001.3 LZ Collaboration

Core of the LZ experiment. Banana for scale.

LZ searches for evidence of dark matter through direct detection. The experiment is designed for particle dark matter of the WIMP variety (weakly-interacting massive particle), and the first science run was able to exclude WIMP’s with a mass of 36 GeV/cm2  and a cross section of 9.2x10-48 cm2 with a confidence level of 90%.

The core of the experiment is a 10-ton liquid xenon TPC (time-projection chamber), situated 1 mile underground in order to reduce background radiation from cosmic rays. Interactions are governed by scintillation within the xenon and are characterized by an initial photon signal denoted S1, and a secondary electron drift signal denoted S2. A typical nuclear recoil event produces on the order of 100 photons and 50 electrons, which are detected by PMT’s at either end of the liquid xenon chamber (circle grids). Interaction position can be interpolated from S1-S2 drift time, and event type (NR, ER, etc.) can be discriminated using the relative sizes of S1-S2 signals.

The small number of detectable particles from an interaction makes the efficiency of the photodetectors crucial for device operation. Optimizing these PMT’s was the core of my research.



P001.4 Thesis Presentation

Presentation Powerpoint

Presentation Recording