2020 July 7

（光学常盤） 再作成か、改造か？再作成のほうが安いかも。 改造部分だけ持参してもらって、追加措置できないか？

共振性能を確認 道村君にも、既存の光学常盤の性能も聞いてみる。

（R&D） Beam Jitter による雑音の見積もりが必要。

QPDの必要性について。

（スケジュール感） R&D インスト―レーション アクセプタンステスト の 3 Phaseで行っていく。

2月から光が取り出せるはずなので、そこから現地での作業は可能。 それまでに、常盤を設置する。 来年6月までにISSができていればいい。

M1の設置で、今までのISSは使えなくなる、

ISSが完成した場合は、アクセプタンステストを設定して、受け渡すが、その場合のKAGRA側の面倒を見る担当が必要。 （SEOで担当決める：宮川君？）

（光学系詳細） 鏡の形状をマテオさんに聞く。 阿久津君と、黒宮君のデータの共有化。

2020 June 3rd

miyoki, michimura, aso, mio, nakano, akutsu, yokozawa, miyakawa, fabian, moriwaki, kuromiya

Kuromiya Plan is here. https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=11722

(1) Today's Discussions on which direction should we go about the future ISS system.

(a)It is important to check what noise is limiting the present ISS floor noise level that cannot be explained with shot noise. If shot noise level can be realized, the obtained ISS level can be below O4 target.

We will use the present laser for O4 (High power one will be put in PSL room). 30W is max as IMC out. The portion for ISS can be enough for O4.

(b)Noise floor below 100 Hz in the present ISS might be due to air fluctuation/beam jitter in the air. This is the first motivation to put ISS detection system in IMMT vacuum tanks. However, this frequency noise can be mainly dominated by other noises, so not so effective for O4, except for several large peaks.

It might be worth noting that intensity noise coupling below 100 Hz is not measured yet. Noise coupling measurement is very important for deriving the requirement for O4, and designing ISS for O4.

(c)The time is so tight to well prepare until O4 judging from the required process, such as design, stuff preparation, demo in Toyama U, demo in KAGRA with stopping laser deliver to KAGRA IFO because the proposed idea requires long preparation time with vacuum opening and adjusting in it.

->

Let's prepare ISS area in another vacuum tank beside IMMT vacuum tank as the final state. Before this state, let's prepare an optical table in the air area at + or - Y position beside IMMT tank for ISS demonstration using the proposed In Vac 4 PD system including optical delivery, stray light damping and so on for these 4 PDs.

We confirmed that there are closed flanges with which we can use for the light delivery for ISS for +/- Y direction in IMMT tank.

In this idea, the beam transmitting through IMMT1 should be divided, one for ISS and the other for IMMT trans monitor, in IMMT tank.

Homework : Please consider which is good, + or - of Y beside IMMT tank for ISS.　You have one week !

(2) Technical Discussions (a)The ultimate intensity noise will be limited by the coupling btw local quantum efficiency difference in PD and beam jitter.

(b)The reduction of beam jitter might be able to improve the present ISS stability level.

(c) 100 mW for in-loop is necessary for future ISS. 200 mW in total is necessary if we also want out-of-loop sensors. We need PD arrays that can receive 200 mW. 4 PDs are enough, not 8 in the original design ? ->

In the air, 4 can be receive 100mW. In vac test might be necessary in Toyama U. Amps for PD are better to be put in vac to avoid terrible electrical noise coupling on PD current. Heat generation might be acceptable even in vac.

(d)Not only main beam but also many many other beam axis such as reverse beam from PRM and its transmitting light, AR reflection light and so on should be considered. for the optical layout design.

(e)Several QPDs should be prepare for adjusting the upstream beam for ISS just after IMMT. Down stream beam will be delivered to 4 PDs.

Ideally, each PD should have each mirror with actuators to adjust the beam spot position in PDs to find low quantum efficiency dependent area in each PD, in addition to several mirrors for global beam direction adjustment for all 4 PDs. In this system, more mirrors are require than the present design that is based on Virgo design.

(f)Be careful not to inject laser in KG5 with high density, otherwise there will be cracked. -> The expected transmitting and reflected light will be small enough.

(g)Be careful SOL-black treatment. It surface is so fragile.