Upgrade scheme of upstream optics for neutron lifetime measurement at J-PARC*

Neutron lifetime is an important parameter in CKM matrix and Big Bang Nucleosynthesis. There is 4.0 sigma difference between two typical method: storage the UCN and detecting the beam of neutron. Therefore, we try to measure the neutron lifetime by using the different method with 1 sec accuracy. Our measurement is carried out at a polarized beam branch on BL05 NOP beam line in the MLF at the J-PARC. We use a time projection chamber (TPC) as a beta-decay detector with little environmental background. We use the device called a spin flip chopper (SFC) to form neutron beam into bunches. The bunches have about half of the TPC length. These devices enable us to detect beta-decay electrons with a 4π solid angle acceptance and achieve good signal-to-noise ratio.
Because SFC couldn't transport enough amount of neutron beam, the experimental sensitivity is limited by the statistic uncertainty. To improve it, we are planning the upgrade of the SFC.  
We simulated the neutron transport system. From simulation results, we can get about 10 times neutron flux by upgrading SFC. We will present details of simulation results and future plan.