• Referee 1

Construction, Qualification, and Commissioning of the ALMA Band 2+ Receiver Cartridges

Overview: An excellent but very expensive proposal, with cost ($16M) which exceeds the entire Development Program budget. Scientifically exciting, well-grounded technically, supported by a superb team.

1. Alignment with NA ALMA Partnership strategic goals;

Matches goal #1.1, "new hardware technologies that improve and extend component, subsystem, and system performance and enhance scientific capabilities", and #1.3, "infrastructure upgrades that increase scientific capability".

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ‘ALMA 2030’ development documents.

The scientific case for Band 2+ is excellent. With demonstrated superb performance over the entirety of Band 2, extending through the lower end of Band 3, the new system would allow observations of low rotational transitions of a number of important cold dense gas tracers (particularly the various deuterated molecules), as well as continuous coverage of extragalactic CO, HCO+, and related molecules at intermediate redshifts. Simply opening up a new band on ALMA is tremendously exciting, extending the range of the world's premier astrochemical engine. The prospects for studies of deuterated molecules in protoplanetary disks seem of special interest, but the breadth of the scientific frontier which would be opened up is, well, breath-taking, ranging from studies of comets to the S-Z effect in galaxy clusters. The scientific gains are clear and compelling; the only real question is whether the funds are available to do this immediately.

While the expansion of Band 2 is not a specific recommendation of the ASAC for ALMA 2030, the opening of a new frequency window, the gain in sensitivity, and the expansion of IF bandwidth is clearly aligned with the spirit of those recommendations.

3. Quality of the upgrade conceptual design; The results from the prototype construction project are impressive, and the proposed improvements (e.g., use of a low-loss silicon lens and removal of the IR filter) should lead to significantly improved noise performance.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

The proposed project is basically ready-to-roll -- the team has clearly done their homework, and their enthusiasm is palpable.

5. Strength of the consortium organization (if applicable); Very strong, both individually (NRAO/CDL + NAOJ) and jointly.

6. Qualifications of the key personnel of the Study; All of those involved are extremely knowledgeable and have extensive experience building various pieces of ALMA. I cannot imagine a better team for this work.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

Again, this is basically the "dream team", with a depth of expertise and experience both in ALMA and in millimeter development generally that other institutions can only envy.

8. Assessment of the level of risk inherent in the design; Very low risk, given the level of prototyping and design that's been done already, combined with the track record of the team.

9. Strength of the Scientific Team supporting the Study; Again excellent. Wootten and Mangum have been carrying the ALMA scientific torch for decades.

10. Level of support guaranteed by the Institutes; No worries on this front.

11. Budgeted cost of the Study; The costing seems reasonable both in itself and in relation to past builds.

============================================================================

  • Referee3
Grade: 1.5

Title: Construction of Band 2+ Receivers

Alignment with NA ALMA Partnership strategic goals

Since Band 2 is the last ALMA band to be implemented, this project has its significance and its science impact would be great. In particular, the frequency coverage would extend into band 3 territories, potentially offering enhancement to observations in the lower part of band 3. The project makes perfect sense to NA ALMA’s strategic goals.

Strength of the scientific case for the proposed ALMA upgrade concept

Because of the high sensitivity offered by ALMA, ALMA is uniquely qualified to do science on cold objects. For the lower part of band 2, there exist very little observation capabilities to cover it. Clearly, the science case is strong for ALMA to develop such a receiver set.

Quality of the upgrade conceptual design

The proposal can be strengthened if the PI can work with European partners, who are working on a parallel band 2+3 proposal. The reviewer has listened to a presentation of the band 2+3 project, and come to the conclusion that the band is too wide for it to be pulled off without sacrificing performance at the band edges, notably at 115 GHz. Nevertheless, by working with these groups, some further technological improvement can be obtained, especially above 90 GHz.

Readiness for production in the context of the ALMA Development Plan

The PI has already devoted a lot of time building engineering prototypes. It seems that they are ready to tackle on the full scale production once certain designs are locked in place.

Strength of the consortium organization

They are working with NAOJ. That makes a lot of sense. As stated above, working with European consortium should be explored.

Qualifications of the key personnel of the Study These people are qualified. Technical expertise, past experience CDL has built Band 6 cartridge. So, they have the past experience to back them up.

Assessment of the level of risk inherent in the design

The proposal shows that the receiver is limited in many ways by the optics. Some further design work is needed. One thing to consider is to use a profile corrugated horn. This may reduce the requirement of the focusing lens. A cold lens would definitely help the performance. The extension above 90 GHz has not been proven. Nevertheless, given the evolution of technology, this should not be too much a hurdle. The PI can also bring the prototype receiver to test at GBT.

Strength of the Scientific Team supporting the Study NRAO has a science team that is supportive of this project. Level of support guaranteed by the Institutes Seems appropriate. Budgeted cost of the Study The cost seems to be acceptable.

  • Referee7
Grade: 2.0

Title: Construction, Qualification, and Commissioning of the ALMA Band 2+ Receiver Cartridges

1. Alignment with NA ALMA Partnership strategic goals;

Alignment with NA ALAMA strategic goals is excellent, in particular the goal of infrastructure upgrades that increase scientific capability.

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ‘ALMA 2030’ development documents.

The science case for implementing Band 2 is clearly set out and described in the proposal. The proposed 8 GHz IF bandwidth is in line with the ALMA 2030 goal to increase the bandwidth of the existing ALMA receivers.

The proposers' assertion that the band 2+ approach is superior to a band 2+3 approach rings true. That is, the performance of band 3, particularly at CO 1->0, should not be compromised, and the science case for band 2 is strong enough on its own to likewise warrant the best possible sensitivity.

Like the original band 2, the proposed band 2+ will cover frequencies down to 67 GHz, where there is significant optical depth in the wing of the 60 GHz O2 band. Although this coverage is driven by the science case, it is worth noting that it may also create opportunities for propagation studies, for example by temperature sounding in autocorrelation during a test observation of a strong point source. Together with the WVRs, this could help disentangle the contributions of wet and dry delay fluctuations. If this was found to be helpful, one could even imagine implementing back-end support to enable the band 2+ receivers to be used for near line-of-sight temperature sounding during observing with other bands. Though this is a speculative notion at this point, it could help improve productivity at the current longest baselines, and help with the push to longer baselines.

3. Quality of the upgrade conceptual design;

Design is already near readiness for production.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

The band 2 prototype has already been qualified, and the changes proposed for the proposed production band 2+ receivers are relatively minor.

5. Strength of the consortium organization (if applicable);

The roles of the partners are well defined and well matched to their respective strengths.

6. Qualifications of the key personnel of the Study;

Key personnel are extremely well qualified.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

Institutionally, the project team is very strong. Of particular relevance for this proposal is that both NRAO and NAOJ have extensive experience with series production as well as deep institutional knowledge of ALMA systems. The Caltech CRAL group has a proven track record in world-leading instrumentation.

8. Assessment of the level of risk inherent in the design;

Technical risk is low given the prototype work as noted above, and the experience the partners have with production and deployment of projects of similar scope.

9. Strength of the Scientific Team supporting the Study;

The proposed work primarily relates to engineering, production, test, and deployment. Nevertheless, the scientific expertise represented on the project team is world-leading.

10. Level of support guaranteed by the Institutes;

Formal institutional letters or statements of support from all partners have not been included with this proposal. Presumably if this large project is approved, this would be part of the formal contracting process.

11. Budgeted cost of the Study;

The budget appears to be realistic. The total project cost yields a cost per receiver cartridge of approximately $225K, which is reasonable.

  • Referee8
Grade: 2.0 because this is a new capability that is part of ALMA baseline science

Title: Construction, qualification, and commissioning of the ALMA band 2+ receiver cartridges PI: Saini

1. Alignment with NA ALMA Partnership strategic goals;

This proposal is a step towards completing the baseline capabilities of ALMA, by adding receivers for band 2. Achieving the ALMA baseline is consistent with the broader goals of the NA ALMA partnership.

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ‘ALMA 2030’ development documents.

Opening up the 67-90/95GHz band is compelling because it allows measurements of the amount of molecular gas at intermediate redshifts. This band also allows observations of fundamental transitions of deuterated and complex organic molecules. The science case is strong in the sense that it is part of the baseline ALMA design. The proposal is consistent with the ALMA 2030 roadmap, and presumably takes priority over upgrades because ALMA 2030 assumes bands 1 and 2 will be completed. The science case in the proposal bounces between band 2, 2+ and 2+3, which is very confusing. There was no explanation of how bands 2+ and 2+3 fit in the overall plan. Has there been a down select, or is there an ongoing competition? This sounds like a mess, and it rather derails the proposal.

3. Quality of the upgrade conceptual design;

The conceptual design of the upgrade seems reasonable, and I do not see any serious technical issues, but this is a major construction proposal, so details really matter. Tables 2 and 3 show performance for variants with Si and HDPE lenses, but why are the amplifier noise temperatures different? The proposal includes a wide band Boifot OMT as an option, but isn’t band 6 being upgraded in part because of problems with this style of OMT?

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

Prototyping of band 2+ cartridges has been completed, so this is the right time to start construction, but the lack of clarity about the choice of lens material and OMT design makes me wonder if the project really is ready.

5. Strength of the consortium organization (if applicable);

NRAO and NAOJ are both strong partners and both have considerable experience in building receivers for ALMA. The amplifiers for the prototype band 2 cartridges were made by CRAL, and the proposal states that CRAL will measure 90LN2A MMICs, but while CRAL appears in the collaborating institutions list (Table 10), there are no costs or contributions. What is going on here?

6. Qualifications of the key personnel of the Study;

The key personnel are well qualified to do the work. Wooten and Mangum have CV’s but are not listed in the staffing tables, and some key personnel do not have CV’s. Morgan at 3% and Srikanth at 1% seem like very small fractions for key engineering staff.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

NRAO and NAOJ have a good track record in this field. Their groups have substantial expertise and experience, and good technical facilities.

8. Assessment of the level of risk inherent in the design;

This should be a fairly low-risk upgrade, given that prototype cartridges have already been built and tested, but I am concerned that the project is as disorganized as the material in the proposal. Maybe the problem is just sloppy proposal writing, but the proposers are asking for $17M. The risk assessment table includes resource constraints as contingency. No. If NRAO wants the work it should sort out its staffing. Contingency is appropriate for unexpected loss of critical staff, but not for absence of critical planning.

9. Strength of the Scientific Team supporting the Study;

The science case for band 2+ is part of the ALMA baseline science case.

10. Level of support guaranteed by the Institutes;

Appropriate.

11. Budgeted cost of the Study;

$17M seems reasonable for implementing band 2+, but given the concerns expressed above, I would fund this only as far as the 8 pre-production cartridges, and then follow up with a rigorous technical review before moving to full production.

  • Supplemental Reviews
  • Referee5

Grade: 3.3

Ready. Case for doing B2 instead of B2+3 is clear. It is too bad that the noise is not yet meeting spec. There is a plan, however, involving both a new wafer and a new lens material. The contingency table doesn’t really deal with the possibility of problems with the ongoing wafer run because it is off-budget here, but if it fails there will be more money needed.

-- AlWootten - 2017-05-09

This topic: ALMA/NAASC > WebHome > ALMADevelopmentProjectReviewMeeting2017 > Band2Plus
Topic revision: 2017-08-03, AlWootten
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding NRAO Public Wiki? Send feedback