HARP: Mixer Bias Performance Investigation and Mixer Spares Production

HARP是一款16单元350 GHz焦平面阵列接收器，于2005年底交付给JCMT。HARP最初主要由STFC以其对JCMT仪器开发方案的贡献的形式提供资金，该方案涵盖了资本要素，此外，还包括支付工作人员的努力，向作为主承包商(提出这一申请的集团)的Cavenish天体物理学提供研究补助金，以及资助UK-ATC的一些分包开发工作。HARP是世界上唯一一个工作在亚毫米波长的同类阵列，其性能是最先进的，可以以迄今闻所未闻的速度绘制大规模的天空地图。它已被JCMT正式接受为设施仪器，现在正在为许多不同的观测方案例行制作数据。在仪器安装、调试和验收(因此关闭了最初的卡文迪什天体物理学补助金)以来的一段时间里，出现了一些与JCMT上仪器的持续操作和维护有关的相对较小的问题，需要引起注意。这项申请提出了一项工作方案，以适当的费用解决这些问题。申请的大部分资金用于支付建造四个新的HARP搅拌机滑块作为“备用”的费用，以及修复三个在调试过程中损坏或出现故障的原始搅拌机滑块的费用。还要求提供资金，以使调查人员能够对已发现在一些哥伦比亚特区发生的虚假振荡的性质和原因进行研究。HARP混合器的偏置条件。这将通过建立一个与天体物理学小组实验室中的HARP几乎相同的实验混合器/LO/IF系统来实现。目标是试图了解这些问题，从而提出改进HARP偏置电子系统的建议，使超导结在直流偏置。目前不可行的水平。人们相信，这将允许实现更低的接收器噪声温度，从而获得更高的灵敏度。

'HARP' is a 16-element 350 GHz focal plane array receiver that was delivered to the JCMT in late 2005. HARP was originally funded largely by STFC in the form of its contribution to the JCMT instrument development programme, which covered the capital elements, plus, to cover the staff effort, research grants to Cavendish Astrophysics as main contractor (the Group making this application) and the funding of some sub-contract development work at the UK-ATC. HARP is the only array of its kind operating in the world at sub-millimetre wavelengths and has a performance that is state of the art, allowing large scale mapping of the sky at hitherto unheard of rates. It has been formally accepted as a facility instrument by the JCMT and is now routinely producing data for many diverse observational programmes. In the period since installation, commissioning and acceptance of the instrument (and hence closure of the original Cavendish Astrophysics grant) a number of relatively minor issues have arisen in relation to the ongoing operation and maintenance of the instrument on the JCMT that require attention. This application proposes a programme of work to address these at a modest cost. The bulk of the funding requested is to cover the costs of building four new HARP mixer blocks to act as 'spares' and repairing three original mixer blocks that were damaged or have become faulty during the commissioning process. Funding is also requested to enable the investigators to undertake a study into the nature and cause of spurious oscillations that have been found to occur at some d.c. bias conditions of the HARP mixers. This would be done by setting up a near identical experiment mixer/LO/IF system to that of HARP in the Astrophysics Group laboratories. The goal would be to attempt to understand the issues and hence suggest improvements to the HARP bias electronics system that would allow the superconducting junctions to be biased at d.c. levels that are currently not viable. It is believed that these will allow lower receiver noise temperatures to be achieved and hence greater sensitivity.