Milestones and Beam Requests

We have outlined a detector and electronics system which is capable of making a high-precision measurement of the positive muon lifetime in a time-structured beam. Our collaboration is capable of carrying out this experiment following a three year plan, commensurate with PSI scheduling.

In the first year following acceptance of this proposal, most of the work will take place at our home institutions. Critical items include: 1) PMT and base testing and selection; 2) Mechanical design of the detector; 3) Engineering stages for the WFD; 4) Prototyping of tiles; 5) Construction of two complete SuperTriangles and a mechanical support 6) Construction of sample targets. Having met these milestones, we will require a test period at PSI as outlined below. The residual polarization of the sulfur target will be compared to that in a non-depolarizing target such as Al.

In the second year, we will complete construction of the µLan Detector and build the WFD. Tests of both subsystems will take place at home institutions. At this stage, the DAQ system will take on a more final form, given the best technology at the time (improvements in tape drives, onboard processors, etc.). The PMTs and bases will undergo a rigorous evaluation prior to installation. Each completed tile will be subjected to uniformity and initial gain settings using a ¹⁰⁶Ru source. We envision constructing a source assembly with a magnetic channel to isolate the high-end of the beta spectrum, near 3 MeV. The clock system will be purchased and tested. At the end of this year, the detector and electronics should be complete. The system will be transported to PSI for debugging using a DC beam. Among critical milestones during the testing will be to further establish the level of residual polarization when using the sulfur target. Conversely, we will use an Al target to measure the level of symmetry in the diametrically opposed tile pairs of the detector. Detailed background studies will be made. Finally, we hope to measure $\tau_{\mu}$ to approximately 20 ppm. If the chopped beam is available, we will make tests of the cycling and measure the effect of dephasing.

In the third year, we expect that PSI will have developed the chopped beam and that the detector and electronics will be complete. Full commissioning and data taking will take place.

An compact list of beam requests and milestones, as presented at the beginning of this document is given next.

1.

Year 1: Use beam line $\pi$E1 with separator tuned for surface muons. Use intensity of up to 10⁶ Hz. Setup includes (1) installation beam counter in vacuum, (2) installation of helium bag with target assembly, (2) installation of two prototype SuperTriangles (scintillator assemblies), (3) installation of laser calibration system, (4) installation of cabling to counting room, (5) installation of electronics and data acquisition system in counting area. Estimated setup time 1 week. Run with depolarizing and non-depolarizing targets. Measure backgrounds. Test ability to cancel forward to backward asymmetry. Request 1 week of beam time.

2.

Year 2: Use beam line $\pi$E1 with separator tuned for surface muons. Use intensity of up to 10⁶ Hz. Install and commission at least half of the µLan Detector. Install ancillary equipment as above. Estimated setup time 2 weeks. Measure $\tau_{\mu}$ to 20 ppm. Request 3 weeks of beam time.

3.

Year 3: Use chopped muon bean line. Use intensity of up to 10⁷ Hz at 10 % duty factor. Install µLan Detector and ancillary equipment as above. Estimated setup time 2 weeks. Commission chopped beam with the µLan Detector. Estimated beam time 1 week. Do production run for lifetime. Estimated beam time 3 weeks. Further steps depend on progress.