  This study presents the recent progress made in developing a spiral fiber
tracker (SFT) for use in the experiment TREK/E36 planned at the Japan Proton
Accelerator Research Complex. This kaon decay experiment uses a stopped
positive kaon beam to search for physics beyond the Standard Model through
precision measurements of lepton universality and through searches for a heavy
sterile neutrino and a dark photon. Detecting and tracking positrons and
positive muons from kaon decays are of importance in achieving high-precision
measurements; therefore, we designed and are developing the new tracking
detector using a scintillating fiber. The SFT was completely assembled, and in
a bench test, no dead channel was determined.
