[Kimura, Yasui, R. Takahashi, M. Takahashi and H. Sawada]
Test period: 2026/04/20~2026/04/21
A vacuum leak test was conducted on the SRM.
A leak of approximately 1×10⁻⁹ Pa·m³/s was detected at the side flange on the +X side of the SRM.
On the other hand, the results of the SRM build-up test showed a rate in the range of 1×10⁻⁴ Pa·m³/s.
Since the difference in leakage rate was significant, a leak test was conducted by blowing helium gas onto all flanges installed on the SRM; however, no new leak points were found other than the side flange.
For reference, a plot of the pressure rise during the build-up test is attached.
Based on the slopes of the straight lines on the double-logarithmic graph (SRM ~ 1, OMMT ~ 0.2), it was determined that the pressure rise in the SRM was due to a leak, while that in the OMMT was due to outgassing.
The build-up value for the OMMT was in the range of 1×10⁻⁷ Pa·m³/s.
[Kimura, M.Takahashi, H. Sawada, R. Takahashi and Tomaru]
On April 22, we continued conducting leak tests on the SRM vacuum vessel.
Since vacuum leaks were suspected due to cracks in the weld lines,
we performed leak tests by blowing helium gas onto the weld lines and using the hood method; however,we were unable to locate the leak. (See attached photo.)
The build-up test was conducted with the SRM and OMMT sharing a common vacuum, and the pressure was recorded using the OMMT’s pressure gauge.
The plot of the build-up test is attached.
The total duration of the build-up test was 935 minutes.
The estimated leak rate from the build-up test was 9.7 × 10⁻⁴ Pa·m³/s.
The slope of the pressure rise was approximately 1.
[Kimura, Tomaru, M. Takahashi, H. Sawada and R. Takahashi]
"Inspection results for the sealing surface of the +X side flange"
A vacuum leak in the range of 1×10⁻⁹ Pa·m³/s was detected, so we inspected the sealing surface of the side flange on the +X side.
As a result, we found a slight scratch on the elastomer surface.
Based on the location of the scratch, we believe it is the cause of the vacuum leak.
After installing a new elastomer on the sealing surface of the +X side flange, the flange was closed.
The flange fastening bolts are currently in a temporarily secured state.
"Inspection results for the sealing surface of the SRM top flange"
After removing the SRM top flange, the condition of the flange sealing surface was inspected.
No dirt or scratches were found on the surface of the elastomer.
Therefore, it was decided to reuse the SRM top flange as a seal.