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| Subject: [LCGT-isc 00258] Re: [LCGT-isc 00254] 論点整理 From: Hiroaki Yamamoto <hiro@ligo.caltech.edu> To: LCGT-isc@icrr.u-tokyo.ac.jp Cc: Norikatsu Mio <mio@hagi.k.u-tokyo.ac.jp> Date: Wed, 11 Aug 2010 00:25:20 -0700 Reply-To: LCGT-isc@icrr.u-tokyo.ac.jp X-Mailer: Apple Mail (2.1081) X-Mew: Text/Plain in Multipart/Alternative as a singlepart |
== Concern on mirror optical losses by H.Yamamoto == |
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| 私としては不可能と信じていますが、一応どの様な表面が必要か。 散乱によるロスは |
* Scattering loss of 45ppm by low-freq (>1mm) surface error of 1nm RMS (25ppm with 0.75nm RMS). * Scattering loss of 6ppm by high-freq (<1mm) surface error of 0.2nm RMS. * Unexplainable punctate scattering loss of 10ppm (realistic estimate would be 15-30ppm). |
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| 鏡の長波長(>1 mm) RMS = 1 nm で鏡あたりの散乱損失が '''45ppm'''. 0.75 nm で 25ppm 鏡の短波長(<1 mm) RMS = 0.2 nm で '''6ppm''' 訳の分からない点状散乱 '''10ppm''' （神様、仏様に祈ってやっと願いがかなうかどうか、15~30ppm が現実的な値） この散乱だけで 61ppm (RMS(長波長)=1nm), 41ppm (RMS=0.75nm) |
These alone would make the total scattering loss already 61ppm (with 1nm LF RMS) or 41ppm (with 0.75nm LF RMS). |
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| シリカの場合、コーティングによる吸収が 0.5ppm 以下が可能と言われているが、表面が汚れると数 ppm 簡単に悪くなる。 この中で、金と時間で解決できるのが長波長領域での散乱ロス。 LIGO は RMS＜0.5 nm を要求し、 Tinsley がそれより良い研磨を達成している。 |
* Besides, absorption at the coatings, assumed to be 0.5ppm, can go worse by a few ppm easily. * LF RMS could be improved if we spend a lot of money and time. LIGO asked for RMS<0.5nm and Tinsley has achieved that value. |
Concern on mirror optical losses by H.Yamamoto
Scattering loss of 45ppm by low-freq (>1mm) surface error of 1nm RMS (25ppm with 0.75nm RMS).
Scattering loss of 6ppm by high-freq (<1mm) surface error of 0.2nm RMS.
- Unexplainable punctate scattering loss of 10ppm (realistic estimate would be 15-30ppm).
These alone would make the total scattering loss already 61ppm (with 1nm LF RMS) or 41ppm (with 0.75nm LF RMS).
- Besides, absorption at the coatings, assumed to be 0.5ppm, can go worse by a few ppm easily.
LF RMS could be improved if we spend a lot of money and time. LIGO asked for RMS<0.5nm and Tinsley has achieved that value.