The MoNA Collaboration Blog

Experiment 09069 in Progress

2010-07-17T13:03:00.000-04:00

Experiment 09069 ( Measurement of Excitation Energy of Neon Prefragments) is under way at the NSCL. The experiment seeks to measure evaporation neutrons in coincidence with residue projectile fragments to determine the excitation energy of the intermediate fragments produced in the reactions. A Mg-32 beam is being used to create neon isotopes that are measured by the Sweeper Magnet and charged particle detectors while the associated distribution of evaporation neutrons is measured using the MoNA detector. Michele Mosby is the spokesperson for the experiment.

Reconfiguration of MoNA

2010-05-27T14:20:00.004-04:00

While reconfiguring MoNA for an upcoming experiment, the students found out just how many cables there are!

Q: How long are all MoNA cables (signal and high-voltage) combined?

(A) 8075 m
(B) 5 miles
(C) as long as the Mackinac Bridge

If you know the answer, write it on a card, attach it to a CAEN V977 I/O register with fully programmable RORA interrupter and individual channel enabling/disabling, and mail it to
1 Cyclotron, East Lansing, MI 48824.

MoNA reconfigured: the modular array was split and detector modules were placed side-by-side in order to achieve a larger angular coverage.

LISA bar attenuation measurement - Westmont College

2010-05-12T19:39:00.009-04:00

Using a 60Co source we measured the spectral location of the 60Co Compton edge as a function of source position along the LISA bar in order to measure the light attenuation. Below are the results for each PMT. Since the total attenuation is dependent on both bulk properties of the material and on the internal reflection profile, the first two points in each plot (i.e those closest to the PMT's) were eliminated from the exponential fits in order to obtain better agreement. The resulting attenuation length for the LISA bar is approximately 5.8 m, in very good agreement with that of the MoNA bars.

First Light - LISA detector spectra from Westmont College

2010-05-06T11:26:00.006-04:00

At Westmont College we've recently complete assembly of our first LISA detector. Pictured below are cosmic muon energy spectra for each PMT, the position spectrum corresponding to the distribution of muons passing through the bar as a function of length, and one of the two detector ends. The position spectrum gate, calculated from the light arrival time difference between the two PMTs, consisted of the AND signal between the two muon peaks.

On another LISA related front, Lewis Elliott and Phil Kasavan are pictured working on the inverter box front panels.

LISA Bars at Concordia

2010-03-12T19:34:00.000-05:00

The scintillation bars continue to arrive at colleges in the MoNA collaboration. The crates containing the 16 bars for Concordia College where delivered today.

First LISA Bars arrive

2010-03-04T21:53:00.000-05:00

The first set of LISA scintillation bars arrived at Westmont College today. The sixteen 2 meter long by 10 cm square bars of scintillation material will form the core of a set of neutron detectors that will be constructed, tested and calibrated at Westmont by undergraduate students. Nine other schools will also build a layer of neutron detector modules for LISA.

Experiment 09040 in Progress

2010-01-27T12:55:00.000-05:00

Experiment 09040: "Study of Neutron Unbound States in 28F" is underway at the NSCL. A Ne-29 secondary beam is being used to create 28F via one proton stripping at the target. MoNA detects the outgoing neutron, the sweeper collects data on the charged fragment and CAESAR measures the gamma-rays. With this information the original 28F state can be reconstructed. This is the first time that that CAESAR has been used in conjunction with the MoNA-sweeper system. The PI for the experiment is Dr. Nathan Frank from Augustana College.

First evidence for a virtual 18B ground state

2009-12-23T10:45:00.006-05:00

The MoNA Collaboration has recently studied the neutron-unbound nucleus ¹⁸B for the first time. ¹⁸B was produced using a ¹⁹C secondary beam from the Coupled Cyclotron Facility at the NSCL. The experimental setup used for this experiment was the standard MoNA/Sweeper setup. The Modular Neutron Array (MoNA) was used for the detection of the emitted neutrons while the charged fragments (¹⁷B) were identified with the help of the sweeper magnet and a series of charged particle detectors. The reconstruction of ¹⁸B presented a dominant s-wave decay at very low energies. The results of this experiment indicate that the s-d mixing observed in heavier N=15 isotones persists in ¹⁸B as well and no clear inversion between the two orbitals can be suggested.

These results were recently published in Physics Letters B.

A. Spyrou at al., Phys. Lett. B, In press

Calem Hoffman Receives 2010 Dissertation Award

2009-11-25T11:44:00.008-05:00

Dr. Calem Hoffman has been chosen to receive the 2010 Dissertation Award by the Division of Nuclear Physics of the American Physical Society for his PhD thesis Investigation of the neutron-rich oxygen isotopes at the drip line. Dr. Hoffman received his PhD from Florida State University under the direction of Professor Sam Tabor. His work on neutron-rich oxygen isotopes was performed using the MoNA-Sweeper facility at the National Superconducting Cyclotron Laboratory. As well as providing important insights into these exotic nuclei Dr. Hoffman made significant contributions to the analysis techniques used with MoNA that will enable other researchers to better understand data from the facility. Some of the results from Dr. Hoffman's work with MoNA/NSCL can be found in the papers listed below:

C.R. Hoffman et al., Phys. Rev. Lett. 100, 152502 (2008).
Determination of the N = 16 Shell Closure at the Oxygen Drip Line

C.R. Hoffman et al., Phys. Lett. B 672, 17 (2009).
Evidence for a Doubly Magic 24O.

Dr. Hoffman will be formally presented with the award at the "April" 2010 Meeting of the American Physical Society in February.

News From the APS Meeting in Hawaii

2009-10-25T11:16:00.003-04:00

Last week, I spent four days in Hawaii attending a joint conference of the American Physics Society and the Physics Society of Japan as part of the Conference Experience for Undergraduates (CEU) program. Staying at the Hilton Waikoloa Village hotel (http://www.hiltonwaikoloavillage.com/ ), I attended presentations on nuclear structure, the quark-gluon structure of the proton, and others. I took an afternoon off one day to travel around the island, where I saw the light of glowing lava reflecting off steam clouds. It was about that time that I become annoyed with myself for forgetting a camera.

Friday, I presented a poster showing the research that I did over the summer, along with over 100 other undergraduate students from across the country and Japan. I was able to see what sort of research other undergraduates do and compare it to my own experience. Also, I learned what sort of questions other researchers ask as professors looked at the posters. All in all, it was a fun learning experience, and I look forward to attending similar conferences in the future.

Eric Lunderberg, Hope College

NSF Awards $1.2M to Collaboration to Build LISA

2009-09-22T15:43:00.000-04:00

The MoNA Collaboration has received a collaborative multi-institution MRI grant to construct the Large-area multi-Institutional Scintillator Array (LISA). LISA, another large neutron detector, will join the Modular Neutron Array (MoNA) and the superconducting dipole Sweeper magnet in the N2 vault. The award, totaling approximately $1.2M, was made to nine of the Collaboration’s undergraduate institutions (CMU, Concordia, Gettysburg, Hope, IUSB, OWU, Rhodes, Wabash, and Westmont) and will continue the Collaboration’s involvement of undergraduate researchers in cutting-edge studies of unstable neutron-rich nuclei. With MoNA-LISA, the Collaboration will be able to more effectively study nuclei with large decay energies and more efficiently measure decays involving multiple neutrons.

MoNA leaves impression on kids

2009-09-18T08:59:00.009-04:00

The N2 vault at the National Superconducting Cyclotron Laboratory, which is the home of MoNA, is often part of tours that visitors to the lab take. A large fraction of these guests are school children. Sometimes they send thank you cards like the one above. Of the many things that they see and hear about while at NSCL, MoNA obviously leaves a lasting impression on them!

Augustana College Joins the MoNA Collaboration

2009-09-16T12:46:00.009-04:00

Dr. Nathan Frank's application to become a member of the MoNA Collaboration was approved at the executive meeting of the collaboration at Beaver Island. Dr. Frank is an assistant professor of physics at Augustana College in Rock Island, IL. He received his PhD from Michigan State University where he played a significant role in the development and construction of the charged particle detectors used with the Sweeper magnet in the MoNA facility. Dr. Frank's recent publication (N. Frank et. al., Neutron decay spectroscopy of neutron-rich oxygen isotopes, Nucl. Phys. A813 199 (2008)) presents results from experiments done at the NSCL using the MoNA/Sweeper facility.

2009 Beaver Island Meeting

2009-09-16T11:14:00.006-04:00

The 2009 MoNA Collaboration Meeting was held at the CMU Biological Station on Beaver Island, MI. The members of the collaboration met over three days to work on data analysis, publications and new proposals. Faculty, post-docs, graduate students and undergraduate students attended as well as some family members.

Disappearance of the N=14 shell

2009-09-01T18:09:00.005-04:00

Using the MoNA detector anexcited state of ²²N unbound with respect to neutron emissionwas observed in a stripping reaction from a 85 MeV/nucleon ²⁶Fbeam at the NSCL. The observed decay energy of 650(50) keV places the level,which is interpreted to be the first 3^- state, atan excitation energy of 1.93(22) MeV. This new measurement combined with previous determinations of the bound state in ²²N indicates a reduction in the N=14 shell gap compared with less neutron-rich isotopes. M. J. Strongman, et. al., Phys. Rev C 80, 021302(R) (2009)