About
The SEparator for CApture Reactions (SECAR) is a next-generation recoil separator system under construction in the ReA3 Hall at the National Superconducting Cyclotron Laboratory and Facility for Rare Isotope Beams (FRIB) at Michigan State University. Click on the image to see the entire system. SECAR is optimized for the direct measurement of capture reactions on unstable nuclei that drive some stars to explode and synthesize crucial nuclei that make up our bodies and our world. The SECAR Project includes work to design, procure, install, and commission this unique system at ReA3. The project was completed on schedule in 2021, and the SECAR Collaboration and other researchers are now planning measurements to improve our understanding of novae, X-ray bursts, supernovae, and other explosive and exotic astrophysical environments.
News
2022.08
A Code of Conduct for the SECAR Collaboration has been
adopted and is
available to view by clicking here.
2022.08
A SECAR Collaboration Workshop was held on Monday, August 8, 2022,
as a satellite workshop at the 2022 Low Energy Community Meeting.
A program for the Workshop
is available by clicking here.
2021.10
The SECAR Project, which began on March 1, 2015,
was completed on schedule and on budget in
September 2021. The entire system has been commissioned
and the key performance parameters have been met.
The SECAR Project Team is very grateful for all the
assistance from DOE, NSF, MSU, FRIB, the review panels,
and our scientific collaborators, their students,
and their home institutions. Extended commissioning
work is ongoing, as are preparations for a series
of upcoming measurements.
2021.09
The first measurements of the
20Ne(alpha,n) reaction
were made with SECAR at the end of August 2021,
successfully observing the 23Mg
recoils at the final focal plane.
Measurements were performed near 2.2MeV/u
for several recoil charge states.
The image below shows recoils from one measurement,
demonstrating excellent rejection of leaky beam.
This is an important achievement in SECAR
commissioning and an important step towards
using SECAR as a tool to measure the cross sections
of (alpha,n) reactions that are important for
astrophysics.
2021.09
SECAR performed the first capture reaction
measurement to test system performance by
measuring a known resonance strength in the
16O(alpha,gamma)20Ne
capture reaction. The goals of the experiment are to
determine the transmission of 20Ne recoils
through SECAR, to measure a known resonance strength,
to determine the rejection of "leaky beam" by the
separator system alone, and then to determine the
"leaky beam" rejection of the combination of the
separator and the focal plane detection system.
The image below shows the identification of
20Ne recoils in the focal plane detector
system; the group of particles below the recoils are
"leaky" beam particles that are completely removed
when a time coincidence is required between the
focal plane signal and the BGO gamma array surrounding
the JENSA 4He gas jet target.
2021.07
The commissioning of the entire SECAR system
is proceeding well. A major milestone was reached
by the first detection of capture reaction recoils
at the SECAR final focal plane detector system.
We bombarded
4He nuclei
in the JENSA gas jet target system with
a beam of 16O from ReA3, and measured
20Ne recoils from the
16O(alpha,gamma)20Ne
capture reaction. Particle identification of recoils
was made at the final focal plane by using the
ionization chamber to measure energy loss and using
a silicon strip detector to measure particle energy.
The system clearly separated 20Ne recoils
from 16O "leaky beam" particles which had
undergone multiple scattering off system components
to make their way to the final focus plan.
beam for an energy measurement. The array of BGO
detectors at the target location were also
successfully operated, and clearly measured
the three expected gamma-ray lines from
the 20Ne deexcitation cascade. Furthermore,
gamma rays were measured in time coincidence with
recoils at the focal plane. This work
demonstrated, for the first time, that all SECAR
components are functioning: the gas target,
target scattering monitors, BGO array, stripper foil,
magnets and Velocity filters, beam diagnostics,
and focal plane detection systems. This work also
demonstrated the successful development of
beam tuning procedures that align the incoming
beam with the SECAR ion optical axis and the
JENSA windowless gas target apertures, as well as
our approach to determine the beam energy
using the previously calibrated first two dipoles
of the SECAR system. The data from this run is
under analysis, and subsequent runs will be made
as the "SECAR Project Completion Experiment."
2021.04
The installation of Velocity Filter 2 was completed, and was
subsequently conditioned up to +/- 130KV. Commissioning runs of
the system continued, for the first time included
all magnets, Velocity Filters, diagnostics, and
focal plane detectors. Velocity Filter 2 was operated
at a total gap voltage of 186 kV in commissioning runs
with a 20Ne beam, and the beam was successfully
transmitted to the final focal plane. Position
spectra of the transmitted beam particles were
collected in the ionization chamber, and the
MCP, ion counter, and DSSD detectors at the
focal plane were all operated successfully.
Schedule
Work will continue on the SECAR "completion experiment"
to measure a known resonance strength in the
16O(alpha,gamma)20Ne
capture reaction. The experiment will also
determine the transmission of 20Ne recoils
through SECAR, and determine the rejection
of "leaky beam" particles both by the separator and
by the combination of the
separator and the focal plane detection system.
The dates of measurements are subject to change based on the facility status.
Please check the SECAR Calendar
for the latest updates. If using a mobile device, please check the
Agenda view shown on the SECAR Mobile Calendar.
Documents
Presentations
Manuscripts
-
"Design of SECAR: a Recoil Mass Separator for Astrophysical
Capture Reactions with Radioactive Beams" by G. Berg, M. Couder,
M.T. Moran, K. Smith, M. Wiescher, H. Schatz, U. Hager, C. Wrede,
F. Montes, G. Perdikakis, X. Wu, A. Zeller, M.S. Smith, D.W. Bardayan,
K.A. Chipps, S.D. Pain, J. Blackmon, U. Greife, K.E. Rehm, and R.V.F. Janssens,
Nuclear Instruments and & Methods A 877, (2018) 87-103.
Newsletters
Other Documents
Sponsors
The SECAR Project is funded by the
Office of Nuclear Physics in the
U.S. Department of Energy Office of Science
and the
National Science Foundation.
Contributions were also made by:
Astrophysics
SECAR will be used to advance our understanding of stellar explosions including novae, X-ray bursts, and supernovae, as well as other exotic astrophysical sites including supermassive stars, hypernovae, Thorne-Zytkow objects, and the very first stars in the Universe. By facilitating direct measurement of reactions on unstable isotopes, SECAR will establish an empirical foundation for simulations of the element creation and energy generation occurring in these fascinating astrophysical systems. For additional details, please see this document on science with SECAR from the 2014 SECAR pre-Conceptual Design Report.
Highlights
2021.07
A major milestone was reached with the SECAR system:
the first detection of capture reaction recoils
at the final focal plane detector system. We measured
20Ne recoils from the
16O(alpha,gamma)20Ne
capture reaction as the "completion experiment" of
the SECAR Project. More details are given above
in the News section.
2018.01
The manuscript "Design of SECAR: a Recoil Mass Separator for Astrophysical
Capture Reactions with Radioactive Beams" by G. Berg, M. Couder,
M.T. Moran, K. Smith, M. Wiescher, H. Schatz, U. Hager, C. Wrede,
F. Montes, G. Perdikakis, X. Wu, A. Zeller, M.S. Smith, D.W. Bardayan,
K.A. Chipps, S.D. Pain, J. Blackmon, U. Greife, K.E. Rehm, and R.V.F. Janssens
was published in
Nuclear Instruments and & Methods A 877, (2018) 87-103.
Separator
The SECAR system consists of 8 Dipole Magnets (red components in the diagram), 15 Quadrupole Magnets (yellow), 5 Multipole Magnets (light blue), and two Velocity Filters (dark blue). The first set of dipole magnets in SECAR performs a critical charge-state selection of both the recoils and unreacted projectiles that enter the SECAR system. The primary projectile rejection components of SECAR are the two Velocity Filters. These devices, also known as Wien Filters, have a vertical magnet field B and a horizontal electric field E that together serve to deflect the trajectory of any particles with a velocity different than E/B. By appropriately tuning these fields, the unreacted beam particles that enter the system can be deflected away while the reaction products of interest (recoils) are passed through to eventually reach the focal plane. Since the unreacted beam particles have an intensity of 1013 - 1017 higher than the capture reaction recoils of interest, the SECAR design includes two Velocity Filters to obtain the level of projectile rejection needed to enable the identification of capture reaction recoils at the SECAR focal plane, and thereby enable the measurement of critical capture reactions on unstable nuclei that power certain types of stellar explosions. More information on the separator can be found in the this SECAR Project Update presentation by Hendrik Schatz (May 2020).
Detectors
The SECAR focal plane features two microchannel plate (MCP) detectors followed by a position-sensitive gas ionization counter. The first detectors will determine the ion velocity by their time of flight, and the second detector will determine the ion atomic number Z by measuring their differential energy loss and total energy loss (dE-E) in the detector gas. The focal plane is designed to give an additional factor of 104 separation of scattered projectile background and capture reaction recoils beyond that provided by the separator magnets and velocity filters.
Targets
The Jet Experiments for Nuclear Structure and Astrophysics (JENSA) system provides 4mm-wide ultra-dense jets of hydrogen and helium gas that serve as the target for capture reactions measurements with SECAR. The high densities possible with JENSA -- over 1019 atoms/cm2 with He -- and the elimination of reactions off of backing materials commonly found in foil targets, makes this gas jet system ideally suited for our experiments. JENSA also functions as a windowless extended gas target that enables searches for resonances with unknown energies to be carried out. Once located, complimentary, higher-resolution studies can be carried out with the jet target. More information on JENSA can be found in this JENSA update presentation by Kelly Chipps (May 2020). Also, please visit the JENSA web site for more details.
Collaboration
NEWS: A SECAR Collaboration Workshop was held on Monday, August 8, 2022,
as a satellite workshop at the 2022 Low Energy Community Meeting.
A program for the Workshop
is available by clicking here.
The SECAR Collaboration is an open, active collaboration of
researchers who are passionate about measuring thermonuclear reactions
that drive some stars to explode. Please
Join Us
if you are interested in contributing to our
separator system or by
submitting a proposal to
enhance our scientific program.
Now that the SECAR Project is complete,
we have transitioned the SECAR Collaboration to
have a focus on proposing, running, and
analyzing experiments. We have now
established a
SECAR Collaboration Agreement
that codifies the activities and organizational
structure of the collaboration.
We have also adopted a
SECAR Code of Conduct
that describes the expectations of the conduct of collaboration
members.
Please click here to learn more
about the SECAR Collaboration.
Please click here to learn more about
submitting a proposal with the SECAR system.
Contact
If you are interested
in Joining the SECAR Collaboration and contributing
to the SECAR system and/or to the scientific program
utilizing this system, please contact one of the members
of the SECAR Collaboration Executive Council:
Manoel Couder, Notre Dame Univ -- Chair
Michael Smith, ORNL -- Communications
or you can contact the following SECAR experts:
Kiana Setoodehnia, FRIB -- SECAR Device Physicist
Hendrik Schatz, MSU
Fernando Montes, MSU
Separator for Capture Reactions
