Minutes of the Alma-Japan Liaison Group, Tokyo, 16-Feb-2000

DRAFT - NOT YET REVISED BY ALG MEMBERS

Present : Ishiguro, Kawabe, Kurz, Napier, Guilloteau

Excused : Brown

Observers : Wootten, Chikada, Nakai, Fukui

The meeting started with a review of collaborations in Phase I.

General :

The list of forthcoming meeting was checked for attendance of Japanese representative. Because of the current meeting could not be attended by R.Brown, it was dediced to have another ALG meeting in Leiden on March 9, just before the ASAC. Reporting of the ALG to the ASAC will occur on March 10.

Antennas :

Proprietary rights limit the diffusion of information. Specifications have been distributed. ICD (Interface Control Documents) have been distributed. The creation of a Japanese ICD for use with Mitsubishi was suggested as action item. This may become an urgent topic if negociations are required. A formal response from Mitsubishi will be asked for.

For the additional small (8-m) antennas, a pre-design study and costing experiment based on common mount re-use should be started. Ultimately, it should be confronted with a dedicated design and cost.

Studies of metrology system is going in parallel in Europe (and US also to some extent). Some information may be restricted due to contractual limitations.

A working group on testing procedures for the antennas should be established. Information exchange about the 10-m antenna at NRO is desirable. Sending a young scientist from IRAM to participate to the 10-m testing was suggested, but turned out to be impractical because of the short notice.

Receiver :

Channel 8 configuration was proposed by Sekimoto san, and is being included in the overall receiver design. It includes SSB, dual-polarisation with a modified MPI as diplexer for the local oscillator injection with low loss.

Common receiver deign is trying to use mirrors (rather than lenses) as much as possible to minimize losses.

Photonics :

There is good progress on high frequency photodetectors. However, the timescale of 2002 is short to convince ourselves that the full photonic solution is viable.

Japan suggest to use the photonic solution up to 300 GHz, with multipliers for higher frequencies.

(« Option 2.7 » as compared to the current « Option 2.3 » which includes photonic only up to band 3).

Parallel development of photomixer and coupling system in Europe is thought valuable for at least another year.

It is suggested to refocus multiplier developments on high frequency multipliers with cooling. Re-emphasis on the development of fixed-tuned tripler is needed.

The development of a photonic reference system, which would improved phase calibration and perhaps remove the need for the round-trip measurement in the LO, is continuing.

Correlator :

Study and prototyping of the A/D converter (« sampler ») is going on at Nobeyama. The goal is 8 GHz clock rate. Note that the test correlator planned to evaluate sampler for ALMA will only work up to 4 GHz (perhaps slightly more).

It is useful to continue parallel development as planned in Europe, but information exchanges would help.

There is a possibility of joining Japan and European efforts if the timescales are of order 2002-2003.

In the second part of the meeting, the draft document on the Enhanced ALMA presented by S.Guilloteau was discussed. A number of small corrections were mentionned.

It was understood that construction by Japan industry of a number of 12-m antennas was essential for participation of Japan to ALMA. Such a construction is not possible on the basis of blue-prints, but requires proprietary design, This will lead to 2 different types of 12-m antennas. This is not considered as a serious problem provided specifications and interfaces are identical. The different set of tools and maintenance procedures is considered as unimportant given the large series which are considered (transporters were not discussed).

Since the total number of antennas is not yet known, it will be important to see what are the ASAC recommendations on the « enhanced ALMA » project.

A cost estimate for Japan participation to enhanced ALMA should be available by end of March (with errorbars [-20 %, +50 %]). Preliminary costing on both sides were presented, but cannot be quoted in writing yet.

Finally, the list of actions and deadlines was reviewed.

Action items :

- Minutes of meetings (S.Guilloteau)

- Revise to documents (S.Guilloteau)

- Implementation plan in Japan (M.Ishiguro)

- Diffusion to ASAC members of these documents

After March 9 (next meeting)

- Finalize recommendation to ACC and NAOJ

- Write global implementation plan (R.Kurz M.Ishiguro)

The final report should be made available to all ACC members no later than March 21.