Minutes of the ISC meeting on 2015/8/24

2015/8/24 14:00 - 15:00

SeeVogh + Kamioka TV conference room

Participants: Nagano, H. Yamoto, Kokeyama, Hirose, Ueda, Aso, Somiya, Arai

Discussions

Simulation

Deadline for deciding the spec. for IBF

• ITM substrate is not in our hands now
• In addition to GTAT, we are asking a Japanese company to make ITM substrate.
• Hirose-san will measure the Japanese sample in Sept.
• If everything goes perfectly well, we need to give the IBF spec. at the beginning of Nov.

• Therefore, the deadline for the simulation is the end of October.

Simulation Scope

Optics data used for simulation

1. Test mass surface maps : Information available are the Zygo pathfinder result and the CSIRO coating on Sapphire. Based on these + educated guess + aLIGO silica mirror maps (~30), make up enough maps to understand the uncertainty.
2. ITM transmission maps : Use data of existing 1 pathfinder sapphire substrate. These maps will be with and without power term subtracted, to see the benefit of IBP.
3. BS : full set available
4. RC mirrors : use polished surface data. No mirror map available after the coating.

What are to be calculated - with and without thermal heating of BS and RC masses

1. PRG and contrast defect of CR and SB
2. Gouy phase in PRC and SRC
3. mode matching of PRC and SRC
4. DC sensing signal related to ASC (RF WFS signals at very low frequency)
5. DC readout signal
6. Cross check with Finesse

Thermal deformation of BS is calculated using COSOL, and the Hello-Vinet formula is used for RC mirrors.

The mode matching calculation will be done

1. calculate the idealistic modes without including mirror aberrations
2. calculate the mode matching at the cold state using maps
3. calculate the mode matching as a function of heating with maps and thermal deformation.

Mode matching is quantified by comparing how much the stationary modes deviate from the idealistic modes on AR side of PRM, SRM and ITMX/ITMY.

Requirements of RoC of mirrors is not the scope of this analysis, i.e., all RoCs in the simulation are those in the KAGRA MIF webpage.

Output Optics

OMC Layout Plan: OMClayout3.pdf

• Current design was presented by Somiya
• Need to double-check the mode calculation (A/I: Aso)
• The vibration isolation requirement for OMC is very strict
  • Will check the requirement for aLIGO (A/I: Arai)
  • Will check the calculation procedure (A/I: Somiya)
• aLIGO does not use the OMC reflection light
• OMC alignment servo bandwidth is around 0.1Hz for aLIGO

Next meeting

2015/9/7(mon) 14:00 -15:00