From soliver at nrao.edu Tue Jul 1 12:09:58 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Tue, 1 Jul 2003 09:09:58 -0700 Subject: [asac][almanews] ALMA Memo 469 Released Message-ID: ALMA MEMO #469 A Broadband Waveguide Thermal Isolator J. L. Hesler , A. R. Kerr ? and N. Horner ? University of Virginia Dept. of ECE, Charlottesville, VA 22902 ?National Radio Astronomy Observatory, Charlottesville, VA 22903 2003-05-30 Keywords: Waveguide components, waveguide transitions, thermal isolators This paper describes a new, compact, waveguide thermal isolator. The isolator is based on a recently developed microwave bandgap joint, a periodic structure which suppresses microwave fields propagating between two parallel conducting surfaces. When such a structure is placed between a pair of waveguide flanges, the flanges can be separated by a few percent of a wavelength before the leakage and mismatch become significant. The thermal isolator is relatively immune to misalignment and cocking. Simulations and measurements on WR-10 thermal isolators indicate excellent performance over the entire waveguide band. The design is readily scalable to other waveguide bands. View a pdf version of ALMA Memo #469. http://www.alma.nrao.edu/memos/html-memos/alma469/memo469.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From ldaddario at nrao.edu Tue Jul 1 14:48:57 2003 From: ldaddario at nrao.edu (Larry D'Addario) Date: Tue, 1 Jul 2003 11:48:57 -0700 Subject: [asac][LamaMemos] New Memo Series for mm/submm telescope technology: LAMA Memos Message-ID: <16129.55193.736037.477351@brador.tuc.nrao.edu> ANNOUNCEMENT OF A NEW MEMO SERIES HOSTED AT THE NRAO A new series of technical/scientific memos called "LAMA Memos" is being created. This series of memos is intended to provide a forum for ideas, results, and discussions related to the technology of millimeter- and submillimeter-wavelength telescopes, including existing instruments and new or proposed instruments such as ALMA. It should be noted that most existing instruments already have their own memo series for specialized reports, and that the ALMA project has a memo series that has recently become supervised and where the content of new memos has become subject to restrictions. LAMA Memos are not subject to any kind of review, so the content of each is the sole responsibility of its author(s). Opinions expressed are not necessarily those of the NRAO nor of AUI nor of any other organization. The title "LAMA" has no special meaning except to provide a distinction between this series and others. By a curious coincidence, the name contains the same four letters as ALMA. To some extent, this series may be regarded as a continuation of the NRAO's MMA Memos, started in 1982 and originally concerned with the Millimeter Array Project that preceeded ALMA. That series had its name changed to "ALMA Memos" after #268, and it remained an unreviewed and unrestricted series up to and including #458. Authors of memos specific to the ALMA Project may wish to continue to submit them to the ALMA Memo Series http://www.alma.nrao.edu/memos . In that case, they will apparently be subject to some level of review prior to posting. The nature and scope of this review has so far not been specified, but recent experience shows that some memos are rejected and the authors of others are asked to make revisions. Criteria for acceptance have so far not been published. Under these circumstances, authors cannot know how to write an acceptable memo, and readers cannot know what level of correctness or quality, if any, has been assured by the review process. Experience also shows that the posting of memos is sometimes substantially delayed. If these conditions are acceptable, submission of ALMA-specific memos to the ALMA Memo Series is recommended. Otherwise, such memos can be submitted to the LAMA Memos Series, where there are no restrictions on content and there should be no significant delay in posting. Further information about the LAMA Memo Series can be found at its index page: http://www.tuc.nrao.edu/~ldaddari/lamaMemos where you will find a link to a page containing instructions for submitting a new memo: http://www.tuc.nrao.edu/~ldaddari/lamaMemos/guidelines.html . Comments and questions about the LAMA Memo series may be directed to me. You are receiving this email because you are a subscriber to the mailing list 'almanews at nrao.edu'. That list is used to announce new ALMA Memos. All almanews subscribers have automatically been made subscribers to the new list 'lamaMemos at nrao.edu' and this list will be used for announcements of new LAMA Memos. If you do not wish to be a subscriber to either of these lists, you should go to http://listmgr.cv.nrao.edu/mailman/listinfo/lamaMemos or http://listmgr.cv.nrao.edu/mailman/listinfo/almanews and follow the instructions for unsubscribing. Similarly, if you have colleagues who would like to join either list, you should advise them to visit one of these pages. Unlike 'almanews', 'lamaMemos' currently allows posting of messages by subscribers, and subscribers are allowed to view the subscriber list. The list is intended only for announcements of new memos and for messages concerning the general management of the memo series. If you are thinking of posting a message, please note that the list is rather long, so it should not be used for any specialized discussion; be sure that your posting is of interest to a *very* wide audience. If traffic becomes unreasonable, the list might be made more restricted. Sincerely, Larry D'Addario ===================================================================== Larry R. D'Addario Research Engineer National Radio Astronomy Observatory Addresses (EMAIL) ldaddario at nrao.edu (PHONE) +1/520/882-8250x123, office; 520/885-8240 home (FAX) +1/520/882-7955 (MAIL) 949 N Cherry Ave, Tucson, AZ 85721-0655, USA. ===================================================================== _______________________________________________ lamaMemos mailing list lamaMemos at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/lamamemos From soliver at nrao.edu Wed Jul 9 14:17:09 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Wed, 9 Jul 2003 11:17:09 -0700 Subject: [asac][almanews] ALMA Memo 462 Released Message-ID: ALMA MEMO #462 Effects of Radiation on the ALMA Correlator Joseph Greenberg (National Radio Astrononomy Observatory) 2003-07-08 Keywords: Waveguide components, waveguide transitions, thermal isolators This memo looks specifically at the effects of cosmic ray radiation at the high ALMA site on the ALMA Correlator. The most vulnerable components of the Correlator are the 17,066 Xilinx Field Programmable Gate Arrays (FPGA). The primary risk is that radiation would cause bits in the downloaded configuration to change. This could change the FPGAs functionality, until reloaded. The most practical remedy is to periodically download the Xilinx personalities. This would reverse the effects of a rare error induced by radiation. View a pdf version of ALMA Memo #462. http://www.alma.nrao.edu/memos/html-memos/alma462/memo462.pdf Download a postscript version of ALMA Memo #462. http://www.alma.nrao.edu/memos/html-memos/alma462/memo462.ps _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at nrao.edu Tue Jul 15 15:48:12 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Tue, 15 Jul 2003 12:48:12 -0700 Subject: [asac][almanews] ALMA Memo 463 Released Message-ID: Variation on the ALMA link design. No Switch, maximum 18km link lengths and the use of an APD. Roshene McCool The University of Manchester 2003-07-07 Keywords: Fiber Optic, Data Transfer, Optical Switch, Photodiode The link design of the ALMA data transfer system currently incorporates an erbium doped fibre amplifier, an optical cross bar switch and will operate over a system specified link length of 25km. Over the course of the ALMA project the optical cross bar switch has been removed from the baseline plan and added to the contingency pool. In addition ongoing work on the Chajnantor site indicates that the maximum fibre link length will be 18km. This document illustrates that the inclusion, or not, of an optical switch and the maximum link length specification are fundamental to the data transfer design. It will discuss how the removal of the cross bar switch and reduced link length will eliminate the erbium doped fibre amplifier from the link design. We show that a variant design using an avalanche photodiode, without an erbium doped fibre amplifier, will operate at the required performance levels. However, whilst the design includes a 6dB start of life margin, there is no additional margin over and above this level. The design is successful, only within strict limits of attenuation outlined in the power budget. Until the fibre optic cable is installed from the antenna pads to the AOS, a degree of uncertainty exists in the attenuation figures of the power budget. Additional attenuation cannot be accommodated in this design, without the use of additional amplification, or a sacrifice of system margin. The existing design, incorporating an erbium doped fibre amplifier has additional margin over and above the 6dB start of life margin and will work with the inclusion of an optical switch and longer link lengths. View a pdf version of ALMA Memo #463. http://www.alma.nrao.edu/memos/html-memos/alma463/memo463.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at nrao.edu Tue Jul 15 15:48:30 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Tue, 15 Jul 2003 12:48:30 -0700 Subject: [asac][almanews] ALMA Memo 468 Released Message-ID: ALMA MEMO #468 Designs of Wideband 3dB Branch-line Couplers for ALMA Bands 3 to 10 Hiroya Andoh (Toyota National College of Technology), Tetsuhiro Minamidani, Norikazu Mizuno, Akira Mizuno, Yasuo Fukui (Nagoya University), Shin'ichiro Asayama, Yoshinori Yonekura, Hideo Ogawa (Osaka Prefecture University) 2003-07-07 Keywords: ALMA bands 3 to 10, wideband waveguide quadrature hybrid, wideband waveguide 3dB 5-branch-line coupler, numerical matrix analysis, S-matrix A guiding principle of design of wideband waveguide 3-dB 5-branch-line couplers for ALMA bands 3 to 10 in suitable for use in SSB heterodyne receivers, their designs and their performances are reported. The couplers have good performances, which maintain an amplitude balance to within 1dB and a phase difference of 89-91 degrees over the frequency range of each ALMA band. The couplers for the ALMA band 3, 4, 5, 6, 7, 8, 9 and 10 include WR-10, WR-6, WR-5, WR-3, WR-2.8, WR-2.2, WR-1.5 and WR-1.2 waveguides, respectively. The couplers are designed by a numerical analytical method by using matrices based on the circuit theory and they are optimized with 3D EM simulator (HFSS). The numerical analytical method for seeking S-matrices mentioned in this memo enables quick calculations for performances of 3-dB branch-line couplers in the case of optimization and possesses advantages over electromagnetic simulation software in common use. View a pdf version of ALMA Memo #468. http://www.alma.nrao.edu/memos/html-memos/alma468/memo468.pdf Download a postscript version of ALMA Memo #468. http://www.alma.nrao.edu/memos/html-memos/alma468/memo468.ps _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at nrao.edu Wed Jul 16 13:08:07 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Wed, 16 Jul 2003 10:08:07 -0700 Subject: [asac][almanews] ALMA Memo 470 Released Message-ID: ALMA MEMO #470 RFI Survey at the ALMA Site at Chajnantor Carla M. Beaudet, Galen Watts, Jeff Acree, Simon J. E. Radford (National Radio Astronomy Observatory) 2003-07-15 A Radio Frequency Interference survey covering 10 MHz ? 18 GHz was conducted at Chajnantor, Chile, the site of the ALMA project, on 2002 December 6 ? 9. The survey provides a ?snapshot? view of existing RF activity in the area. The detected signals fell into these categories: noise from nearby electronic equipment, broadcast TV and FM radio, and terrestrial and satellite radio services. View a pdf version of ALMA Memo #470. http://www.alma.nrao.edu/memos/html-memos/alma470/memo470.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at nrao.edu Thu Jul 17 17:58:36 2003 From: soliver at nrao.edu (Stacy Oliver) Date: Thu, 17 Jul 2003 14:58:36 -0700 Subject: [asac][almanews] ALMA Memo 471 Released Message-ID: ALMA MEMO #471 Site Properties and Stringency Neal Evans (U. Texas), John Richer (MRAO Cambridge), Seiichi Sakamoto (NRO, Japan), Christine Wilson (McMaster, Canada), Diego Mardones (Universidad de Chile), Simon Radford (NRAO, Tucson), Selby Cull (NRAO, Tucson), Robert Lucas (IRAM) 2003-07-03 Keywords: Site, Stringency, Atmosphere In summer 2002, the ALMA Coordinating Committee (ACC) charged the ALMA Science Advisory Committee (ASAC) to address the following issue: "The ASAC is asked to evaluate all available site (225 GHz opacity, 12 GHz phase stability, 350 micron and >1 THz) data for Chajnantor, and to discuss any significant trends and issues which may impact the scientific mission, design or mission emphasis of the baseline instrument" This memo contains the ASAC working group's response to this charge. It was originally included in an appendix to the ASAC report of October 2002, and is here released as a memo to give it a wider audience. View a pdf version of ALMA Memo #471. http://www.alma.nrao.edu/memos/html-memos/alma471/memo471.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews