Speaker
Description
The anomalous magnetic moment ($g-2$) of the muon can be determined with high precision both theoretically and experimentally, providing a sensitive test of the Standard Model. The consistency between theoretical predictions and experimental results is still under discussion and requires further verification on both sides. The electric dipole moment (EDM) of the muon, which violates time-reversal symmetry, is predicted to be vanishingly small in the Standard Model. Therefore, the observation of a finite value within experimental sensitivity would be a clear signal of new physics. Although it has not yet been observed, improving the experimental upper limit can place stringent constraints on various new physics scenarios.
The J-PARC muon $g-2$/EDM experiment aims to provide an independent measurement of the muon $g-2$ from previous results of BNL and FNAL by employing a new experimental approach. In addition, it seeks to measure the muon EDM with a sensitivity of $10^{-21}\,e\cdot\mathrm{cm}$, thus enabling either the discovery of new physics or significant constraints on theoretical models.
In this experiment, using muon cooling and acceleration, we generate a $300\,\mathrm{MeV/c}$ low-emittance muon beam and store it in a compact storage ring with a highly uniform $3\,\mathrm{T}$ magnetic field. The decay positrons from the stored muons are detected by a silicon strip detector installed inside the storage region. The detector consists of 40 modules arranged radially around the center of the ring. The reconstructed trajectories of the positrons enable precise measurements of the anomalous spin precession of the muon, from which $g-2$ and the EDM are extracted.
The detector system must satisfy stringent requirements, including high-rate capability, minimal disturbance of the magnetic field, and precise sensor alignment. The readout component of the detector consists of ASIC boards, FPGA-based Readout Boards for the SliT detector (FRBS), mirror-symmetric FRBS, and DC-DC converters. The detector is installed in a low-vacuum region ($<0.1\,\mathrm{atm}$), separated from the high-vacuum muon storage region by a Kapton window. Since the readout components are expected to dissipate a total of $8.5\,\mathrm{kW}$, an active cooling system is required to maintain the detector below the operational temperature limit of the ICs, while ensuring temperature stability within $\sim 8\,{}^\circ\mathrm{C}$ to prevent thermal deformation that would affect the EDM sensitivity of $10^{-21}\,e\cdot\mathrm{cm}$.
We report the design of the cooling system and its performance assessment based on both experimental measurements and finite element analysis.
| Position | Student |
|---|---|
| Affiliation | The University of Tokyo |
| Country | Japan |
