From cwhite at NRAO.EDU Mon Jul 2 16:44:00 2001 From: cwhite at NRAO.EDU (Carolyn White) Date: Mon, 2 Jul 2001 16:44:00 -0400 (EDT) Subject: [asac] [almanews] ALMA Memo No. 377 Released Message-ID: Design and Fabrication of Quartz Vacuum Windows With Matching Layers for Millimeter-Wave Receivers Daniel Koller, A. R. Kerr, G. A. Ediss, and D. Boyd 2001-Jun-25 Sensitive radio receivers operating at frequencies above approximately 100 GHz require the use of cryogenic detectors, often SIS mixers, cooled to liquid helium temperatures. A vacuum window is required to couple the radiant energy through the chamber walls to the detector element with as little loss as possible. While seemingly simple to make, the optimization of windows for high transparency and low leak rate is a non-trivial problem requiring the construction of multilayer dielectric structures. The Atacama Large Millimeter Array (ALMA) telescope, to be built in Chile, will require over 600 vacuum windows covering ten frequency bands. In support of ALMA and its own in-house development needs, NRAO has developed a number of crystal quartz vacuum windows utilizing Zitex, Goretex, Teflon and other plastic anti-reflection coatings to improve the window's overall transmission within specific bands. The design, fabrication details and testing of some of these windows are discussed. View a PDF version of ALMA Memo #377. http://www.alma.nrao.edu/memos/html-memos/alma377/memo377.pdf ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From soliver at tuc.nrao.edu Tue Jul 3 15:30:33 2001 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Tue, 3 Jul 2001 12:30:33 -0700 Subject: [asac] [almanews] ALMA Memo No. 379, 380, and 382 Released Message-ID: ALMA Memo #379 SUMMER CLIMATE OVER CHAJNANTOR Ricardo Bustos 2001-JUL-03 A description of the main characteristics of the Bolivian High and what is now called the South American Monsoon System (SAMS) is presented. The water origin for the Altiplano can be inferred from both descriptions, being this supply mostly from the Amazon basin. From this premise, an analysis of ground weather station data and radiometers data from Chajnantor was performed. View a pdf version of ALMA Memo 379. http://www.alma.nrao.edu/memos/html-memos/alma379/memo379.pdf ____________________________________________________________________________ _____________ ALMA Memo #380 The Correlator at the OSF? Bryan Anderson and Roshene McCool University of Manchester, Jodrell Bank Observatory 2001-07-02 This document is intended to provide some costings which could influence the location of the correlator in the final ALMA system. It discusses some design details but it does not constitute a final design. It provides a snapshot with current, small-quantity prices of components which suppliers claim to be be available and deliverable. Some components which would improve the design do not seem to be available despite much advertising. Some of the figures have come from distributors in the UK where traditionally there has been a tendency to convert US $ prices into ? Sterling by changing the symbol but not the number. The costings are broadly indicative but will not necessarily be accurate in detail. It is hoped that the other parts of the cost trade offs will tip the scales in favour of a minimum-cost solution. View a pdf version of ALMA Memo 380. http://www.alma.nrao.edu/memos/html-memos/alma380/memo380.pdf ____________________________________________________________________________ _____________ ALMA Memo #382 MM-VLBI with ALMA Melvyn Wright(Radio Astronomy laboratory, University of California, Berkeley), Geoff Bower(Radio Astronomy laboratory, University of California, Berkeley), Don Backer(Astronomy department, University of California, Berkeley), Alan Whitney( Haystack Observatory) 2001/06/27 Keywords: VLBI, phased array, Polarization, recording technology, correlators This memo reviews the requirements for using the ALMA array as a part of a global VLBI array at millimeter wavelengths. ALMA can be outfitted for VLBI at modest cost and should be planned with this capability in mind, as it may be more difficult to retrofit at a later date. The essential features required in the ALMA design are discussed. View a pdf version of ALMA Memo 382. http://www.alma.nrao.edu/memos/html-memos/alma382/memo382.pdf ============================================================================ = ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From cwhite at NRAO.EDU Fri Jul 6 17:01:35 2001 From: cwhite at NRAO.EDU (Carolyn White) Date: Fri, 6 Jul 2001 17:01:35 -0400 (EDT) Subject: [asac] [almanews] ALMA Memo 381 Released Message-ID: ALMA Memo No. 381 Elements for E-Plane Split-Block Waveguide Circuits A. R. Kerr 2001-Jul-05 E-plane split-block waveguide construction is well suited to many millimeter-wave components, including power dividers, frequency multipliers, and single-ended, balanced and sideband-separating mixers. Recent ALMA memos have described quadrature hybrids and a matched power divider suitable for split-block construction. This memo describes four additional waveguide elements which can be used as building blocks in more complex circuits: a compact H-plane bend, a short E-plane bend, a matched E-plane Y-junction, and a broadband transducer from full- height waveguide to quartz suspended stripline. The components are suitable for fabrication on a CNC milling machine using an end-mill of diameter equal to the waveguide height, and do not require the insertion of separate waveguide short-circuit pieces at the ends of waveguides. Prototype designs are given for WR-10 waveguide (75- 110 GHz), which can be scaled for any other waveguide size with the same 2:1 aspect ratio. View a PDF version of ALMA Memo #381. http://www.alma.nrao.edu/memos/html-memos/alma381/memo381.pdf Download a postscript version of ALMA Memo #381. http://www.alma.nrao.edu/memos/html-memos/alma381/memo381.ps ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From awootten at NRAO.EDU Tue Jul 10 17:20:30 2001 From: awootten at NRAO.EDU (Al Wootten) Date: Tue, 10 Jul 2001 17:20:30 -0400 (EDT) Subject: [asac] Telecon Thursday 12 July 1415 UT Message-ID: <200107102120.RAA20307@polaris.cv.nrao.edu> Folks: Here's the dial-in information for the telecon: CALL DATE: JUL-12-2001 (Thursday) CALL TIME: 10:15 AM EASTERN Daylight TIME 1415 Universal Time USA #: 888-566-6192 International #: +1-712-257-2398 PASSCODE: ALMA LEADER: Dr. Al Wootten The draft agenda may be found at: http://www.cv.nrao.edu/~awootten/mmaimcal/asac/asacjul01agenda.html In lieu of Karl Menten as he recovers, Peter Schilke will join us. Clear skies, Al +--------------------------------------------------------+ | Alwyn Wootten (http://www.cv.nrao.edu/~awootten/) | | Project Scientist, Atacama Large Millimeter Array/US | | Astronomer, National Radio Astronomy Observatory | | 520 Edgemont Road, Charlottesville, VA 22903-2475, USA | | (804)-296-0329 voice Help us build The ALMA| | (804)-296-0278 FAX {> {> {> {> | +----------------------------------^-----^-----^-----^---+ From awootten at NRAO.EDU Wed Jul 11 10:39:51 2001 From: awootten at NRAO.EDU (Al Wootten) Date: Wed, 11 Jul 2001 10:39:51 -0400 (EDT) Subject: [asac] Operations Materials Message-ID: <200107111439.KAA08581@polaris.cv.nrao.edu> FolksDear ASAC Members: Shortly, Carolyn White will mail the binder of operations materials to you. It includes: 1) Project Book Chapter 18 (available on the WWW if you don't have it already) 2) Mark Gordon's plan of May 2000 with revisions 3) Vol 6 of the ESO Proposal (I think you have this) 4) ALMA Memo No 367 (probably of most interest to ASAC) 5) Recommended Location of the ALMA Operations Support Facility: The Direct Link Option (Hofstadt, Hardy and Brown Feb 2001) Would ASAC members please check their addresses at http://www.alma.nrao.edu/committees/ASAC/ and send any corrections to cwhite at nrao.edu so that these hefty binders will go to the correct place. Thanks! Clear skies, Al From soliver at tuc.nrao.edu Wed Jul 11 13:09:47 2001 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Wed, 11 Jul 2001 10:09:47 -0700 Subject: [asac] [almanews] ALMA Memo 335 Released Message-ID: ALMA Memo #335 Phase Drift Measurements of YIG-Tuned Oscillator Sources for the ALMA LO Dorsey L. Thacker, Eric W. Bryerton, Richard Bradley, and Kamaljeet Saini 29 June 2001 In this memo, we present measured phase drift data of a YIG-tuned oscillator (YTO) multiplied to mmwave frequencies, a prototype of the baseline ALMA LO source. The test setup and analysis algorithms are described. We also discuss phase drift added by mmwave multipliers and power amplifiers, with the conclusion that their contribution is insignificant. Various components and system concepts are analyzed with respect to their contribution to the phase drift of the array. As phase drift at the level required for ALMA is unique and not well understood, much of the discussion will be of a tutorial nature. View a PDF version of ALMA Memo #335. http://www.alma.nrao.edu/memos/html-memos/alma335/memo335.pdf ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From ewine at strw.leidenuniv.nl Wed Jul 11 16:10:51 2001 From: ewine at strw.leidenuniv.nl (ewine at strw.leidenuniv.nl) Date: Wed, 11 Jul 2001 22:10:51 +0200 (MEST) Subject: [asac] DRAFT DSB/2SB recommendation Message-ID: <200107112010.WAA29923@deuterium.strw.leidenuniv.nl> Dear ASAC, Below please find a very ROUGH DRAFT of our DSB/2SB recommendation to the project. Thanks to Geoff for the preparation. Please read carefully and send comments to me and Geoff. We'll discuss it briefly tomorrow at our telecon. Talk to you all soon, Ewine **************************************************************************** Issues Associated With DSB versus SSB Receivers for the Initial ALMA Complement A number of ALMA memos (numbers 168, 170, 301, and 304) and reports by the project scientists to the ASAC have recently considered the potential sensitivities of double sideband (DSB) versus a number of single sideband (SSB, which here includes variants such as sideband separating, or 2SB, approaches) receiver designs. While the conclusions differ to some extent, the numbers and general trends driving the potential decisions are similar and are worth summarizing: -The potential sensitivity gains with various SSB options are greatest for observations of transitions in a single IF sideband or for observations of lines in separate sidebands where the needed correlator capacity is less than that available. -The potential sensitivity gains with SSB receivers increase as the receiver noise contribution to the total system temperature decreases. That is, SSB receivers provide improved performance as the atmosphere begins to dominate the overall noise. -For continuum or wideband spectral line observations that "fill up" a correlator bandwidth matched to that available from the DSB receiver IF, SSB receivers with the same IF bandwidth are sometimes less sensitive because the DSB bandwidth is effectively sqrt(2) larger. With the current estimates of achievable receiver noise temperatures, the estimated improvements in system temperatures with SSB receivers range from 1.4-1.2 (low frequencies to high) for observations in a single sideband (Memo 304, Figure 2). As receiver noise temperatures drop, the improvement attainable with SSB receivers gets larger. Under the same conditions, continuum observations with DSB receivers are more sensitive, particularly at high frequencies. It is worth stressing, however, that with better receivers SSB approaches will be equal to or superior to DSB receivers for all observing modes, and that the potential improvement corresponds to a very large number of additional antennas. Recent work at submillimeter frequencies has demonstrated that the SIS mixers themselves can operate near the quantum limit, and that in the future it will be possible to build receivers that are much more sensitive than those likely to be initially installed on ALMA as our understanding of materials at THz frequencies improves. At that point, SSB receivers will clearly be superior, especially if their IF bandwidths can be made sufficiently large to occupy most of an atmospheric window and fill a very large correlator with a single sideband (and with dual polarization receivers). In the meantime, the overall gains (or losses) in sensitivity with SSB versus DSB receivers are a complex function of the assumed receiver temperatures, the atmospheric conditions under which observations are performed, the correlator capabilities, and the temporal mix of observing modes used by the array. It is largely differences in these parameters that drive the differences in the various ALMA memos and reports. SSB receivers also are more complex to design, build, and maintain, and so if the gains are small or negligible then DSB receivers provide better value from a total project perspective in terms of cost and risk, especially early in the project lifetime. Given the likely pace of design and development after ALMA construction, it seems unavoidable that both DSB and SSB receivers will be implemented on the array at some point. It is therefore important for the project not to preclude either option at this time, at least in terms of making decisions now that make it extremely expensive to implement new receiver layouts in the future. Some specific recommendations, by no means exhaustive, might include: -Dual polarization, DSB receivers provide the best alternatives for bands 8-10 at present, and should be the baseline design. The correlator(s) must therefore provide for phase switching demodulation of the upper and lower receiver sidebands. -Design and development of SSB receivers is critical for ALMA and should continue. Decisions on when it is appropriate to implement SSB designs, especially for the lower frequency bands which are likely to have SSB implementations ready first, are best made by the Receiver and System IPTs. The ASAC requests regular updates on the progress in this area, especially as regards the first light receiver bands. -The IF distribution and correlator downconverter systems should not preclude the introduction of SSB (read 2SB) receivers, or at least should not make the conversion to SSB/2SB approaches prohibitively expensive. -The cryostat design, cryogenic systems, and interfaces should be compatible with a gradual migration from DSB to SSB receiver cartridges. From awootten at NRAO.EDU Fri Jul 13 17:11:51 2001 From: awootten at NRAO.EDU (Al Wootten) Date: Fri, 13 Jul 2001 17:11:51 -0400 (EDT) Subject: [asac] Chilean travel, safety precautions Message-ID: <200107132111.RAA21436@polaris.cv.nrao.edu> Dear ASAC members and ALMA ASAC attendees: As you plan your travel, you may find it helpful to consult the travel tips page Mark Gordon wrote: http://www.tuc.nrao.edu/mma/sites/Chajnantor/region/travel-tips.htm (though this is a little outdated now) and the site safety rules http://www.aoc.nrao.edu/~pnapier/mmasafety.htm and general information on high altitude safety http://www.tuc.nrao.edu/mma/sites/Chajnantor/altitude/ Clear skies, Al +--------------------------------------------------------+ | Alwyn Wootten (http://www.cv.nrao.edu/~awootten/) | | Project Scientist, Atacama Large Millimeter Array/US | | Astronomer, National Radio Astronomy Observatory | | 520 Edgemont Road, Charlottesville, VA 22903-2475, USA | | (804)-296-0329 voice Help us build The ALMA| | (804)-296-0278 FAX {> {> {> {> | +----------------------------------^-----^-----^-----^---+ From awootten at NRAO.EDU Fri Jul 13 17:32:51 2001 From: awootten at NRAO.EDU (Al Wootten) Date: Fri, 13 Jul 2001 17:32:51 -0400 (EDT) Subject: [asac] Oops Message-ID: <200107132132.RAA21909@polaris.cv.nrao.edu> My last message was missing a crucial character (the trailing l): Mark Gordon wrote: http://www.tuc.nrao.edu/mma/sites/Chajnantor/region/travel-tips.html Apologies and thanks Mick for pointing this out. Clear skies, Al From ewine at strw.leidenuniv.nl Sat Jul 14 03:33:07 2001 From: ewine at strw.leidenuniv.nl (Ewine van Dishoeck) Date: Sat, 14 Jul 2001 09:33:07 +0200 Subject: [asac] Chile reservations Message-ID: <200107140733.JAA13703@strw.LeidenUniv.nl> Dear ASAC members, Below please find the reservations for the Chile meeting. Please send comments or changes to Leo Bronfman. The hotel problem in San Pedro has been solved. Any other burning ASAC issues should be sent to the vice-chair Geoff Blake (gab at gps.caltech.edu) in the next three weeks (up to August 5) since I will be out of e-mail contact. Happy summer! Ewine ********************************************************************** RESERVATIONS ALMA SAC San Pedro Santiago SEPTEMBER Baars Jacob + 1 8 9 10 11 12 13 Bachiller Rafael 7 8 9 10 11 12 13 Booth Roy 8 9 10 11 12 13 Benz Arnold 8 9 10 11 12 (6 7) Blake Geoffrey 8 9 10 11 12 Bronfman Leonardo + 1 8 9 Chikada Yoshihiro + 1 8 9 10 11 12 13 Evans Neil + 1 7 8 9 10 11 12 13 Glendenning Brian 8 9 10 11 12 13 Guillateau + Dutray 8 9 10 11 12 13 Gurwell Mark 11 12 Kurtz Richard 9 10 11 12 Lucas Robert 8 9 10 11 12 13 Matsuo Hiroshi 9 10 11 12 13 Nakai Naomasa 10 11 12 Payne John 8 9 10 11 12 13 Radford Simon 8 9 Richer John 8 9 10 11 12 13 Shaver Peter 8 9 10 11 12 13 Tetematsu Ken 10 11 12 van Dishoek Ewine 8 9 10 11 12 13 Walmsley Malcolm 10 11 12 13 Welsh Jack 8 9 10 11 12 Wilson Christine 8 9 10 11 12 Wootten Al + 1 8 9 10 11 12 13 Yamamoto Satoshi 10 11 12 Crutcher Richard 9 10 11 12 13 Mangum Jeffrey 8 9 10 11 12 13 Cox Pierre 8 9 10 11 12 13 Glendenning Brian 8 9 10 11 12 13 Hasegawa Tetsuo (8 9) 10 11 12 From soliver at tuc.nrao.edu Fri Jul 27 12:28:09 2001 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Fri, 27 Jul 2001 09:28:09 -0700 Subject: [asac] [almanews] ALMA Memo 383 Released Message-ID: ALMA Memo #383 A Simple Technique for Disciplining Independent Demultiplexers Marc Torres and Olivier Gentaz IRAM (Grenoble) , France 2001-07-26 In every antenna of the ALMA array, the digitizers will deliver 3-bit (or more) samples at the rate of 4 Gigasamples per second. Data is not practical to handle at this speed and needs to be converted to a lower frequency by means of serial-to-parallel conversion. To solve this problem the telecomm industry has developed fast "mux/demux" chips, which unfortunately are single-bit devices. If we use 3 (or more) of them, a synchronisation problem arises. The right way of solving this problem would be to design a chip including 3 (or more) demultiplexers on the same die. Should this approach be found not economical for ALMA, this paper describes a method for synchronizing several single-bit commercial demultiplexers. A prototype circuit including two single-bit devices has been built and successfully tested. The measured timings for acquisition and recovery are presented. View a pdf version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma335/memo335.pdf Download a ps version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma335/memo335.ps ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From cwhite at NRAO.EDU Fri Jul 27 14:18:54 2001 From: cwhite at NRAO.EDU (Carolyn White) Date: Fri, 27 Jul 2001 14:18:54 -0400 (EDT) Subject: [asac] [almanews] Correction to Memo 383 Release Message-ID: ALMA Memo #383 A Simple Technique for Disciplining Independent Demultiplexers Marc Torres and Olivier Gentaz IRAM (Grenoble) , France 2001-07-26 In every antenna of the ALMA array, the digitizers will deliver 3-bit (or more) samples at the rate of 4 Gigasamples per second. Data is not practical to handle at this speed and needs to be converted to a lower frequency by means of serial-to-parallel conversion. To solve this problem the telecomm industry has developed fast "mux/demux" chips, which unfortunately are single-bit devices. If we use 3 (or more) of them, a synchronisation problem arises. The right way of solving this problem would be to design a chip including 3 (or more) demultiplexers on the same die. Should this approach be found not economical for ALMA, this paper describes a method for synchronizing several single-bit commercial demultiplexers. A prototype circuit including two single-bit devices has been built and successfully tested. The measured timings for acquisition and recovery are presented. View a pdf version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.pdf Download a ps version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.ps ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. From soliver at tuc.nrao.edu Fri Jul 27 14:28:20 2001 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Fri, 27 Jul 2001 11:28:20 -0700 Subject: [asac] [almanews] ALMA Memo 383 Released- corrected links Message-ID: ** The last announcement had the incorrect links to the memo...here are the corrected links. ALMA Memo #383 A Simple Technique for Disciplining Independent Demultiplexers Marc Torres and Olivier Gentaz IRAM (Grenoble) , France 2001-07-26 In every antenna of the ALMA array, the digitizers will deliver 3-bit (or more) samples at the rate of 4 Gigasamples per second. Data is not practical to handle at this speed and needs to be converted to a lower frequency by means of serial-to-parallel conversion. To solve this problem the telecomm industry has developed fast "mux/demux" chips, which unfortunately are single-bit devices. If we use 3 (or more) of them, a synchronisation problem arises. The right way of solving this problem would be to design a chip including 3 (or more) demultiplexers on the same die. Should this approach be found not economical for ALMA, this paper describes a method for synchronizing several single-bit commercial demultiplexers. A prototype circuit including two single-bit devices has been built and successfully tested. The measured timings for acquisition and recovery are presented. View a pdf version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.pdf Download a ps version of ALMA Memo 383. http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.ps ============================================================================ = ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body. ============================================================================= ALMAnews is a broadcast service. To unsubscribe, send an e-mail message to majordomo at nrao.edu with "unsubscribe almanews" in the message body.