LU|ZONE|UL Collection:https://zone.biblio.laurentian.ca/handle/10219/21412024-03-28T14:35:04Z2024-03-28T14:35:04ZExtracting the time of core-bounce from core-collapse supernova neutrino signals in current and next-generation neutrino detectorsHill, Remington W.https://zone.biblio.laurentian.ca/handle/10219/40902024-03-28T07:09:36Z2023-09-25T00:00:00ZTitle: Extracting the time of core-bounce from core-collapse supernova neutrino signals in current and next-generation neutrino detectors
Authors: Hill, Remington W.
Abstract: Core-collapse supernovae (CCSNe) are amongst the most rare and energetic events in
the galaxy. In the Milky Way, they are predicted to happen as infrequently as 1.64±0.46
times per century. Over a duration of approximately ten seconds, a CCSN will convert
≈ 99% of its iron core’s gravitational binding energy into neutrinos. The initial wave of
neutrinos is powered by the neutronization burst, which is generated by electron capture
reactions on the collapsing core, which follows a critical time in the dynamics of a CCSN,
core-bounce. It has been 36 years since a CCSN was observed via its neutrinos. With
the observation of SN 1987A via its neutrino signal, a global effort has been undertaken
to bring together all neutrino detectors under a common goal: providing an early alert to
the astronomical community of an impending supernova and, if possible, triangulate to
the CCSN using its neutrino signal. This effort is called the SuperNova Early Warning
System (SNEWS). Triangulation simulations have recently seen tremendous success in
determining where a supernova is positioned from its neutrinos, but these studies have
made use of high statistics detectors such as HyperK, JUNO, and DUNE. This work im-
plements six analytic techniques into the detectors HALO and HALO-1kT, with the intent
of extracting a common reference time across all detectors to use for triangulation efforts.
The common reference time chosen is the time of core-bounce (t0), as it is followed by a
rapid rise in νe events within νe sensitive neutrino detectors. Our analysis made use of the
SNOwGLoBES event rate calculator, which quantifies event rates from supernova neu-
trino signals, which was then simulated through each detector’s Monte Carlo simulation
code. Various supernova models were taken into consideration to account for systematic
uncertainties between different mass progenitors, equations of state, etc. Our analysis
determined that for HALO and HALO-1kT, a constant fraction discriminator (CFD)
technique was optimal in extracting the time of core-bounce from the neutrino signal at
close distances (< 3 kpc), while a negative log likelihood technique was optimal at further
distances. At 1 kpc, HALO-1kT had a precision of 543 μs when using the CFD technique
to extract t0, which falls within the precision required to triangulate effectively (< 1 ms,
which HALO-1kT can obtain out to 3 kpc). With the intent of eventually implementing
these techniques into all experiments involved in SNEWS 2.0, SNO+ was incorporated
into our analysis in the later stages of this research. A preliminary exploration showed
severely degraded performance in contrast to HALO-1kT, where the CFD technique could
only obtain millisecond precision, not microsecond. Further analysis is encouraged.2023-09-25T00:00:00Zsno+ background study: polonium on acrylic vessel surface and radon assayYu, Shengzhaohttps://zone.biblio.laurentian.ca/handle/10219/40632024-03-28T07:09:07Z2023-01-18T00:00:00ZTitle: sno+ background study: polonium on acrylic vessel surface and radon assay
Authors: Yu, Shengzhao
Abstract: SNO+ is a 780 tonnes organic liquid scintillator neutrino detector located at Vale’s
Creighton mine, Sudbury, ON. 2 km overburden of rock above helps to achieve the low
cosmic radiation background level of SNO+. Meanwhile, radioactive material in the rock
can decay and produce radiation in the region of interest for the search of 0νββ decay. SNO+
is looking for neutrinos at very low energy and thus it is crucial to have a low background
environment. My thesis evaluates two kinds of background sources: 222Rn and 210Po. 222Rn
is the progeny of 238U in the rock. The water and gas assays are used to monitor the 222Rn
concentration in the surrounding cavity water and other parts of the experiment or other
gas volumes in SNOLAB. The analysis of the SNO+ data helps to understand the 210Po
activity on the internal surface of the detector’s acrylic vessel. The 222Rn level in the cavity
water is below the target of 4.5 × 10−13 gU238/gH2O. The Rn levels in the LN2 plant and
international dewar are at a 10−4
reduction factor compared to mine air. The 210Po background level in the internal AV is holding a relatively constant level of about 1800 events
per second. Spatially, the 210Po backgrounds are more active at the equator and the belly
plate regions. The estimated number of 210Pb atoms deposited on the AV inner surface is
1.84 × 1012
.2023-01-18T00:00:00ZHALO-1kT prototype He-3 counters: background studiesWeima, Estherhttps://zone.biblio.laurentian.ca/handle/10219/40002024-03-27T07:36:54Z2023-02-09T00:00:00ZTitle: HALO-1kT prototype He-3 counters: background studies
Authors: Weima, Esther
Abstract: The last supernova near our galaxy was in 1987. HALO-1kT will be a low background galactic
Supernova detector. HALO- 1kT needs to have low backgrounds to detect a supernova on the far
side of the galaxy. A big source of backgrounds is the planned 4.3 km of helium-3 proportional
counters. My research tested the prototype proportional counters to ensure their backgrounds are
low enough to avoid regular false positives. The first way of testing them was to take the 4 counters
underground at SNOLAB to collect 3-4 months of data as well as a 2-day calibration run to see
what the base background rate is. Two of the counters were then attached to electrostatic counters
and counted to determine the background of the wall material. Those results showed emanation
rates of 0.137 Hz to 0.811 Hz in the wall material. While that is clean, it is not clean enough to
meet HALO-1kT background goals.2023-02-09T00:00:00ZEvaluating 238U external background for SNO+ experiment using radon Aasays and 214Bi analysisHussain, Syed Muhammad Adilhttps://zone.biblio.laurentian.ca/handle/10219/38672024-03-27T07:36:29Z2022-04-11T00:00:00ZTitle: Evaluating 238U external background for SNO+ experiment using radon Aasays and 214Bi analysis
Authors: Hussain, Syed Muhammad Adil
Abstract: SNO+ is large multipurpose detector located at SNOLAB filled with liquid scintillator.
The scintillator will then be loaded with Te isotope, allowing to look for neutrino-less double
beta decay which is extremely rare. This will determine if the neutrino is its own antiparticle.
One of the main concerns for these rare event experiments is the presence of backgrounds,
which could mask the signals of interest. This thesis will focus on 222Rn, one of the most
common backgrounds due to its excessive prevalence in the mine environment. Radon decays
into daughter nuclei where the energies lie within the region of interest for neutrino-less double
beta decay. The detector is housed in a large cavity that is filled with ultrapure water and has
a nitrogen cover-gas in order to avoid contamination. Radon Assay is a technique that was
developed for the original SNO experiment to keep track of the radon content within the cavity
and the covergas systems. The Assay system itself is well calibrated with low backgrounds.
Assays are performed frequently at different positions of the cavity and cover-gas to monitor
the radon levels. During a radon assay, radon is cryogenically trapped, concentrated, and
shared into a ZnS coated Lucas cell for a period of time and known amount of flow. This
Lucas cell is then connected to a PMT, which detects the decayed alphas that are used to
calculate the number of radon atoms in the assay. This technique is a crucial part of measuring
and monitoring the low backgrounds for the experiment which is then verified from the in-situ
Bi214 analysis for accuracy.2022-04-11T00:00:00Z