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| . Subject: [LCGT-isc 00258] Re: [LCGT-isc 00254] 論点整理 . From: Hiroaki Yamamoto . To: LCGT-isc at icrr.u-tokyo.ac.jp . Cc: Norikatsu Mio . Date: Wed, 11 Aug 2010 00:25:20 -0700 </pre> |
== Concern on mirror optical losses by H.Yamamoto == |
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| * 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 point scattering loss of 10ppm (realistic estimate would be 15-30ppm). |
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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 * 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, 0.5ppm based on the LMA coating on Silica substrate, can easily go worse by several ppm by contamination. * LF RMS could be improved if we spend enough money and time. LIGO set the requirement to be 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 point 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, 0.5ppm based on the LMA coating on Silica substrate, can easily go worse by several ppm by contamination.
LF RMS could be improved if we spend enough money and time. LIGO set the requirement to be RMS<0.5nm and Tinsley has achieved that value.