Display the Experiment Proposals for S1065

Experiment: S1065

Weak Nucleon-Nucleon Interactions by Parity Non-Conservation Measurements in Francium

by the FrPNC group

Pending (Stage 1)
Spokespersons:
G. Gwinner (University of Manitoba)

Original Proposal for EEC meeting 200512S

Table of Contents

Detailed Information

Proposal/Report S1065_proposal.pdf (1.31 MB)

Beam Shift Summary

12-hr ShiftsBeam Line / channelPolarized Primary BeamPriority
New Beam Requests
 299 BLA2A/ISAC No
Committee Recommendations
 0 No H

This proposal aims at measurements of nuclear anapole moments using a novel method that is sensitive to the parity violating interference between hyperfine microwave transitions and optical Raman transitions in isotopes of Francium. The proponents have developed a rather elaborate plan based on an early suggestion of Sandar and later developed mostly for parity-violation searches in hydrogen. These are well-motivated experiments, which probe the parity-violating nucleon-nucleon couplings. There is much interest in the nuclear community for understanding the PV nucleon couplings and for resolving apparent experimental discrepancies in this area. The Committee was impressed with the elegance of the experimental plan and its difficulty. A great deal of off-line work will be necessary to demonstrate the viability of the method. The proponents intend to accomplish this in critical off-line experiments with Rb. It is essential that a demonstration of the robustness of the method should be accomplished before large blocks of running time are committed to the projects. The Committee regards this as an important part of a broader program of experiments that will be made possible once actinide targets are available at TRIUMF. The present proposal fits into the portfolio of Francium experiments with actinide targets as described by the presenter. The Committee regards the fundamental physics experiments that will be possible with actinide targets as a high priority for TRIUMF.

Recommendation: The Committee endorses this experiment with high priority. However, allocation of running time should be done at a future time. We suggest that the entire Francium program receive a special review once the other Francium proposals are available. This review should provide guidance for staging and executing the program, taking account of manpower, resources and the timeliness of each component of the program.


Membership

G. Gwinner University of Manitoba Professor 40 % Spokesperson

Basic Information

Date Submitted
2005-11-18 15:35:50
Date Experiment Ready
0000-00-00
Projected Completion Date
0000-00-00
Summary *

The researchers will conduct a measurement of the anapole moment in Fr. The anapole moment of a nucleus is a parity non-conserving (PNC), time reversal conserving moment that arises from weak interactions between the nucleons. Its measurement is a unique probe for neutral weak interactions inside the nucleus. The anapole can be detected in a PNC electron-nucleus interaction and reveals itself as a nuclear-spin dependent signal. The proposed measurement of the nuclear anapole moment will be by direct excitation of an E1 transition within the ground state hyperfine manifold. This transition is parity forbidden, but is allowed by the anapole-induced mixing of opposite parity states.

This proposal combines precision measurement techniques from atomic, molecular and optical physics with the forefront understanding of low-energy nuclear structure for the elucidation of the weak interaction in a chain of Fr isotopes, where the effect is predicted to be one order of magnitude larger than in Cs. We will place ≈ 106 trapped atoms at the anti-node of a standing microwave/RF field and measure the population transferred by the parity forbidden E1 transition. A highly synergetic, optical parity experiment will complement the microwave/RF measurement.

The project will have as a first benchmark the laser trapping and cooling of Fr atoms on-line at ISAC. The researchers have ample experience in the construction, commissioning and operation of magneto-optical traps for francium. The second step will require the transport and confinement of the trapped atoms into a region of controlled electric and magnetic fields to interrogate the atoms. The TRINAT collaboration has experience in such transfer of radioactive atoms. This environment will allow us to detect the PNC signature. Extensive studies of systematic effects will ultimately permit the extraction of the anapole moments of Fr isotopes with 10% accuracy, constraining parity non-conserving meson-nucleon couplings. In particular, measurements in isotopes with unpaired neutrons will be sensitive to a different combination of weak meson-nucleon couplings compared to the one extracted from Cs and Tl data.

Plain Text Summary *
Primary Beam Line
An electronically shielded, temperature-controlled room in a location to be determined in the ISAC low-energy area.
Primary Beam and Target
500 MeV protons, unpolarized;
UC2 or ThC2, 1-100 μA protons
Secondary Channel
ISAC LEBT
Secondary Beam
Mass-separated ≤ 30 KeV, isotopically clean francium ion beams from ISAC.
TRIUMF Support (Resources Needed)

•Beam line to deliver ≤ 10 keV francium ions to a neutralizer.
• Electromagnetically shielded enclosure in experimental hall with temperature control and air filter for lasers and rf equipment, 5.5 m by 6 m.
• Mechanical design help for radiation shielding in the neutralizer region.

Other Funding

• NSERC, Tests of fundamental symmetries with ultra-cold radioactive atoms and cold ions in traps and storage rings (G. Gwinner); support has been granted through April 2006; continuing support through April 2008 has been applied for. • NSF (USA) Anapole moment studies in francium (L. A. Orozco); support has been granted through June 2007.
• NSERC TRINAT project grant (J.A. Behr, K.P. Jackson, M. Pearson); support has been granted through April 2006; continuing support through 2009 has been applied for.

Safety Issues

Yields of > 108 /sec short-lived Fr alpha emitters will be delivered to the main ISAC floor. Most of the activity is alpha radiation and will be contained in the trap region. Mechnical design support will be requested for lead or heavymet shielding near the trap volume. Mechanical pump exhausts will be filtered using the experience gained from the E929 radon EDM experiment tests with xenon. Certain masses produce long-lived 206;208;209;210Po and will require careful precautions as polonium is quite volatile. The safety officer will be M. Pearson, who has experience gained at experiments at ISOLDE and at Stony Brook.

Proposals and Progress Reports

200512S (Original Proposal)