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News from the Nuclear Science Division at Berkeley Lab
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Nuclear Science Division Newsletter
In this issue:October, 2016

Majorana Demonstrator Presents First Results

Art McDonaldFigure 1. The spectrum between 1838 and 2238 keV after all cuts from DS1.
Art McDonaldFigure 2. Low energy uncorrected spectra from natural (blue) and enriched (red) detector data from DS0. Cosmogenic isotopes in the natural detectors produce the 10.3-keV 68Ge, the 8.9-keV 65Zn, and the 6.5-keV 55Fe X-ray peaks along with the tritium beta decay continuum. The FWHM of the 10.3-keV peak is ~0.25 keV.

At the Neutrino 2016 conference in July, the Majorana Collaboration released initial results from the first of two modules in the Majorana Demonstrator, which is operating at the 4850-ft level at Sanford Underground Research Facility in Lead, SD.

Neutrinoless double-beta decay (NDBD) search is the only viable technique to test whether neutrinos are their own anti-particles. The Majorana Demonstrator is an array of high-purity germanium detectors that aims to search for this decay and to demonstrate the feasibility of a much larger experiment with significantly better sensitivity to this lepton-number-violating decay (a sensitivity of ~15 meV in Majorana mass).

The LBNL Majorana group is responsible for the procurement and production of the enrGe detectors and the design and fabrication of the signal readout electronics.

The two modules in the Majorana Demonstrator contain 35 detectors with a total mass of 29.7 kg, fabricated with Ge enriched to 88% in 76Ge and 15.1 kg fabricated from natural-Ge (7.8% 76Ge). The 74.5% yield of converting initial material into Ge diodes is the highest achieved to date.

Data from two data sets were presented at Neutrino 2016. The first data set (“DS0”) was acquired from June to October 2015, and represents the commissioning of Module 1. Final low-background shielding and vacuum sealing were installed during the acquisition of the second data set (“DS1”), which is the first physics production running from late December 2015 to mid-April 2016. The 76Ge exposures are 1.37 kg-y for DS0 and 1.66 kg-y for DS1.

As Figure 1 shows, after all cuts to remove instrumental backgrounds, alpha and beta-gamma backgrounds from intrinsic radioactivities in DS1, 5 counts remained in the 400-keV window centered on the 76Ge double-beta decay endpoint of 2039 keV. The level corresponds to 23+13-10 counts/ (ROI ton year) at the 68% CL. No events fall within the 3.1-keV full-width-half-max region of interest near the endpoint. We set a lower limit on the NDBD half-life of 3.7x1024 years (90%CL).

Figure 2 shows the low-energy spectrum for DS0. The enriched detectors show a significantly lower event rate, due to the efforts to minimize the detectors’ exposure to cosmic rays during the production process. The lower backgrounds and the ultra-low noise electronics allow the data to be used to search for other physics phenomena beyond the Standard Model, such as bosonic dark matter interactions and solar axions.

Efforts are now focused on commissioning Module 2, accumulating more data in both modules and on improving the analysis to better reject backgrounds. The expected background within the region of interest is still low enough that NDBD half-life limit should increase nearly linearly with exposure. With about 30 kg of 76Ge, we project a NDBD half-life sensitivity of ~1026 years with 3 to 5 years of data.

CUORE Towers are Completely Installed

The detectors were installed in a customized cleanroom to protect them from naturally occurring radioactivity.
Bottom view of the towers.

The CUORE collaboration achieved a major milestone on August 26, 2016, with the successful installation of all 19 towers, consisting of 988 individual TeO2 crystals and weighing almost 750 kg (1650 lbs), in the cryostat. This assembly was performed in a customized clean room, filled with air that was filtered to remove radon gas (a contaminant that would reduce the sensitivity of the CUORE detector). This clean room and the air filtering system was designed and assembled by members of the Berkeley Lab. CUORE will soon begin a month-long cool-down that will be soon followed by recording the first data.

CUORE (Cryogenic Underground Observatory for Rare Events) is an Italy-US-China ton scale bolometric detector located at the Istituto Nazionale di Fisica Nucleare Laboratori Nationali del Gran Sasso in Italy. The goal of CUORE is to search for the neutrino-less double beta decay of 130Te, which if observed, would establish the Majorana nature of the neutrino and provide information on the absolute mass scale of the neutrino. CUORE members from the Nuclear Science Division include staff scientist Brian Fujikawa, faculty senior scientist Yury Kolomensky, and postdocs: Benjamin Schmidt and Bradford Welliver; along with Joseph Wallig and Sergio Zimmerman from Engineering.

NSD staffers showcase Diversity, Inclusion, and Pride

During the month of June, several members of Nuclear Science Division staff participated in the organization and planning of the Berkeley Lab’s Lambda Alliance Employee Activity Association (go.lbl.gov/lambda), Lambda Alliance Employee Resource Group, and the Diversity and Inclusion (D & I) Office’s Pride Month Events.

These events, the first of their kind at LBNL, were supported and attended by staff of all levels throughout the entire laboratory. NSD’s participation showcased the commitment to diversity and inclusion in our division and to that of the entire laboratory.

The Pride Month Networking event was the highlight of the month’s events, which wouldn’t have been possible without the generous support from members of the NSD staff such as Division Director Barbara Jacak, and Division Safety Coordinator Marty White.

Tom Gallant, Lady Idos of the Diversity and Inclusion Office, and Amanda Kreiger of Engineering organized the event as a collaborative effort. The group is seen pictured below along with the Lambda Alliance Employee Resource Group’s Executive Sponsor and Associate Laboratory Director for Biosciences, Jay Keasling, and Laboratory Director Michael Witherell.

The event, which was intended to bring people of all levels together throughout the lab, was well attended by NSD staff as well. Pictured below are Chun Ho Chow who volunteered for several of the month’s events, and Deborah Wang with co-organizer Tom Gallant. Special thanks to Erika Suzuki from the Applied Nuclear Physics program for creating the registration site

Other events included a movie screening of ‘The Danish Girl’, with the promotional poster created by NSD’s Sandy Ritterbusch, and a Resource Fair with booths by Rainbow Community Center of Contra Costa County, the Pacific Center in Berkeley and UC Berkeley Employee Assistance.

A final collaborative event that was organized by the Diversity and Inclusion office and the Lambda Alliance was a Diversity and Inclusion Brown Bag session. This event, which was chaired by the D & I office, was made possible with the volunteer participation of the Division D & I Council Members which includes representation from every Division. NSD’s own Ernst Sichtermann participated in the panel of council member representatives and regularly supports the diversity and inclusion discussions on behalf of the division.

Fragments

 
UC Davis graduate student and long-term LBNL visitor Kathryn Meehan, has been awarded the 2016 Gertrude Scharff-Goldhaber Prize, consisting of $1,000 and a certificate. The award was established by the Brookhaven Women In Science organization to recognize promise and accomplishment in a female graduate student conducting their thesis research at Stony Brook University or Brookhaven National Laboratory (BNL). Meehan is a member of the STAR Collaboration working under Professor Daniel Cebra's (UC Davis) guidance and collaborating with Grazyna Odyniec (LBNL). Her work focuses on an analysis of charged particle spectra, as part of STAR’s Fixed-Target Program which aims to clarify the nature of the transition from hadronic matter to a QGP by extending the Beam Energy Scan II Program to lower energies than what is feasible in collider mode. She is currently one of a team of students and professors working on a paper that compares results from a STAR 2015 Au + Au fixed-target test run to previous results with fixed-target data taken at a similar collision energy.

 

 

The MAJORANA group welcomes new postdoctoral fellow Dr. Jordan Myslik. A Sudbury, Canada, native, Jordan obtained his BSc degree in Mathematics and Physics from the University of Toronto.  During his undergraduate years, he spent several summers researching on supernova-neutrino detection and low-level counting at SNOLAB in his home town.  Recently he completed his PhD dissertation at the University of Victoria on a simultaneous fit of neutrino and antineutrino data from the T2K near detector.

 

 

On August 11, some 100-odd NSD staffers and friends gathered for the annual 88 inch barbeque. In honor of the occasion, the 88 inch halls were turned into dining halls, while, outside, volunteers grilled hamburgers and hot dogs.

 





Newsletter Notes
Please send any comments, including story suggestions to Spencer Klein at srklein@lbl.gov.
 
Previous issues of the newsletter are available at:
https://commons.lbl.gov/display/nsd/NSD+Newsletter.
Copyright © 2016 Berkeley Lab, All rights reserved.


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