= Satellite Meeting on Future Upgrade of KAGRA =
[[LCGT/Meeting/f2f/2019August|Main F2F Page]]

== Date/Time/Venue ==
August 21th (Wed.) 13:00 - 16:10
(We would like to finish the main discussions by 15:30, when [[LCGT/Meeting/f2f/2019August#Tour|the KAGRA site tour]] starts)

Venue: Multi purpose room (多目的ホール), [[http://www.sci.u-toyama.ac.jp/EN/aboutus/guide.html|Faculty of Science]], [[https://www.u-toyama.ac.jp/en/access/gofuku/index.html|University of Toyama, Gofuku Campus]]

('''''Note that different from the venue of F2F meeting''''', [[LCGT/Meeting/f2f/2019August#Venue|Kuroda hall]])

Zoom(2) connection: https://zoom.us/j/6676627462

Anyone are welcome to join the discussions on site or via online and for even those who didn't make a registration.

== Related information ==
 * [[LCGT/Meeting/f2f/2019Apr/FuSat|The last satellite meeting in April/2019]]
 * [[http://gwwiki.icrr.u-tokyo.ac.jp/JGWwiki/KAGRA/KSC/FPC|FPC wiki]]
 * [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9590|FPC White Paper]]

== Program ==
||<rowbgcolor="#E0FFFF"16%  style="text-align:center">Time ||<style="text-align:center">Subject and Title ||<24%  style="text-align:center">Speaker ||File ||
||<rowbgcolor="#FFFFE0" rowstyle="text-align:left;                ">13:00-13:10 ||||<style="text-align:left;">'''Introduction''' || ||
|| ||Introduction from FPC ||S. Haino and FPC ||[[#Agenda|(↓)]]||
||<rowbgcolor="#FFFFE0" rowstyle="text-align:left;                ">13:10-14:00 ||||<style="text-align:left;">'''Mirror and Cryogenics''' || ||
|| ||Sapphire Mirror||M.Leonardi,T.Tomaru||[[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10568|o]] ||
|| ||Heat extraction||T.Yamada,T.Tomaru||[[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10569|o]] ||
||<rowbgcolor="#FFFFE0" rowstyle="text-align:left;                ">14:00-16:00 ||||<style="text-align:left;">'''Upgrade plans''' || ||
|| ||Upgrade plans and publication||S. Haino and FPC ||[[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10567|o]]||
----

<<Anchor(Summary)>>
== We would like to get agreements (understandings) by KAGRA collaborators on: ==
 * Due to the ITM issues, O5 plans should be more realistic (DRSE 150 Mpc ~ BRSE+FDsqz 170 Mpc)
 * Define and share the ultimate goal 
(100~200 kg TM 300~500 Mpc ?) towards 2030’s
 * White paper (WP) will be two parts: (1) Survey and list of facts and (2) Recommendation of plans and science scenario
 * WP(1) to be officially approved [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9590|JGW-M1909590]]
 * WP(2) will be drafted by October for the internal review by KAGRA in/by Dec. F2F, and eventually 
to be published after KAGRA joins O3
 * WP can be referred for funding requests/proposals

/* By considering the current ITM issue, KAGRA/KAGRA+ configuration in O5 to be BRSE+FDsqz (170 Mpc) with DRSE (150 Mpc) as a backup => this is a Broad-band option */
/* Define the ultimate goal of KAGRA towards 2030's (until 3G observation starts) with heavy mass (100~200 kg) and high power (350~500 W) laser to achieve 300~500 Mpc sensitivity. => this is a broad-band option */
/* The strategy and path between O5 and ultimate can be discussed according to the technological feasibility and science cases */

<<Anchor(Minutes)>>
== Minutes (by K.Yamamoto and SH) ==
 * Sapphire mirror issue (M. Leonardi)
   * iLM(Geppo) is on last stage but his original proposal does not mention birefringence.
   * Now iLM is interested in studying birefringence issue => could be the best solution
   * For near future (O4), 200ppm/cm absorption can be accepted.
   * Internal stress causes birefringence ? Annealing parameter of vendor are not known.
   * ITM for O4 : By re-polishing and same time coating, finesse unbalance could be solved, but birefringence can not be solved (same order of magnitude). 
   * Is it worth ? Budget and schedule should be considered. Evaluation by commissioing is necessary (which (finesse unbalance or birefringence) is large must be known).
   * Or fused silica for O4 ? -> coating thermal noise could be an issue. Suspension improvement is necessary. Thermal compensation system is necessary.
   * Silicon test mass ? -> still far future ?
   * IBF (Ion Beam Figuring) can solve only 1 DoF (S-pol) out of 2 (S,P-pol)

 * Heat extraction capacity (T. Yamada)
   * Thermal resistance must be reduced and possible (factor 2) at least for the contact ones.
   * For the sapphire fiber, temperature dependence of thermal conductivity is not taken into account.
   * About 10 K/W out of 35 K/W are from sapphire fiber
   * Heat link is x2 longer than original design
   * 35 K/W may be achieved

 * Upgrade plans and publication (S. Haino)
   * ET fixed with 1.5 um wavelength which CE2 is aiming at 2 um which have advantage in the scattering
   * Publication plan -> First purpose of FPC is PREPARATION of white paper.
   * For the publication, we have to discuss EO (about feasibility, budget, schedule)
   * WP should be prepared for the coming budget proposal, and contribution from FPC is expected ?
   * We should remove the recommendation part from the first release to make it as list of facts 
   * Realistic option for O5(perfect 22 kg mirror and FDSQZ) proposed is minimum success.
   * Silicon mirror changes a lot of thing.
   * Ultimate goal of KAGRA (final BOSS)
   * Boundary condition must be defined at first.

<<Anchor(Agenda)>>
== Agenda ==
 * Things happened since [[LCGT/Meeting/f2f/2019Apr/FuSat|the last satellite meeting]]
   * O5 plans (A+,AdV+) and schedule are [[https://dcc.ligo.org/LIGO-P1900218/public|released to public]]
   * Schedule of 3G (ET, CE) released in [[https://agenda.infn.it/event/15928/|GWADW 2019]]
   * A new proposal [[https://indico.ego-gw.it/event/20/contributions/401/attachments/292/432/DEM_DAWN5_Oz_roadmap_v2.pdf|ozGrav-HF]]
   * [[http://ilm.univ-lyon1.fr/index.php?option=com_content&view=article&id=973|iLM]] submitted a proposal to produce large sapphire bulk up to 200~250 kg and aiming low heat absorption (< 10ppm/cm)
   * ITM birefringence issue found (e.g. [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10369|JGW-G1910369]],[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10495|JGW-G1910495])
   * Science study updated by A.Nishizawa [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9934|JGW-G1909934]] by considering LVK network

 * We have a session dedicated to sapphire mirror and heat extraction
   * Understand the current status of sapphire mirror issues and future prospects
   * Maximum laser power is limited (at least) by the heat absorption and heat extraction capacity. We should understand the current estimation. 

 * We would like to get agreement/understanding on the followings:
   * Publication on the KAGRA future upgrades
   * Define the ultimate goal in long term towards 2030's
   * More realistic plans for O5

 * Publication plan (Full KAGRA author)
   * Serve as the 2nd release of the white paper
   * Discussion about the ultimate goal and intermediate plants including O5
   * Share the same idea inside the collaboration as well as to inform it to LV and near-by communities
   * Submission/publication target just after KAGRA manage to join O3 (late 2019~early 2020 ?)
   * Target journal: PRL or PRD ? (depending on the number of pages/figures) c.f. iKAGRA => [[https://academic.oup.com/ptep/article/2018/1/013F01/4817346|PTEP]], bKAGRA-ph1 => [[https://iopscience.iop.org/article/10.1088/1361-6382/ab28a9|CQG]]

 * Ultimate goal of KAGRA
   * Time scale around 2030
   * It should fill the gap between O5 and 3G
   * 200 kg Sapphire as the primary candidate (iLM may help us a lot if their proposal is accepted)
   * Backup plan with Silicon ? Decision tree should be prepared
   * With 200 kg sapphire and 500 W laser, 500 Mpc may be possible [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10533|JGW-G1910533]]
   * What is the name ? Naming is important: hKAGRA ? (hyper-KAGRA, or h as Heavy-mass and High-power), uKAGRA ? (ultimate-KAGRA) or dKAGRA ? (dream-KAGRA)

 * More realistic plans for O5
   * Due to the ITM issues it may be difficult to achieve the design sensitivity during O4 
   * One option is to achieve the design sensitivity (with detuning) of 150 Mpc in O5
   * Detuning doesn't go well with squeezing. Should we give up detuning but BRSE with FD squeezing (60m filter cavity ?)
   * High Freq. (HF) upgrade requires R&D and change of suspensions which may have a risk to worsen the sensitivity, while FD squeezing can be installed independently so that we can go back to detuning option if the installation of squeezing doesn't finish in time