1.
Professor A. Hopkins
Australian Astronomical Observatory
105 Delhi Road
North Ryde
New South Wales 2113
Australia
11th
February, 2015
Direct line +44 (0)1235 446719
Local fax +44 (0)1235 446362
E-mail brian.ellison@stfc.ac.uk
Dear Professor Hopkins,
Letter of recommendation for Mr Pawala Ariyathilaka for a AAO Student Fellowship Summer
Placement
It is my pleasure to write to you in support of Pawala Ariyathilaka’s application for a Student Fellowship
(summer placement) at the Australian Astronomical Observatory (AAO).
Pawala worked as an industrial placement sandwich course student within my research and development
group (the Millimetre-wave Technology Group) at the Rutherford Appleton Laboratory (RAL) and during
the period Aug 2013 to July 2014. His placement was in part fulfilment of a BSc degree course that he is
currently completing at the University of Cardiff, and within the School of Physics and Astronomy.
During his time within my group, Pawala demonstrated a strong willingness to learn, and keenness to
develop his skills and experience. He supported my group’s millimetre-wave technical development
programme, which is directed towards the provision of instrumentation for astronomical and atmospheric
remote sensing, with great enthusiasm. In particular, he undertook a difficult and demanding role
associated with the development of new test and measurement infrastructure for a millimetre-wave half-
wave-plate (HWP) polarisation rotation filter. The HWP device is a key component within a future
spaceborne cosmic background exploration experiment, and the test system allows room and low
temperature measurement of its polarisation performance.
In support of the above, Pawala designed a diffraction limited optical interface to couple a millimetre-
wave power source to a detector, and between which the HWP is placed for measurement and
performance evaluation. The test and measurement procedure also requires location of the HWP within a
vacuum chamber and on a cryogenic (~15K) surface. Consequently, it proved necessary for the interface
to preserve the vacuum integrity of the cryostat unit, whilst simultaneously allowing propagation of the
millimetre-wave signal into and out of the chamber.
The work required Pawala to gain an understanding of long wavelength optics, polarisation devices,
cryogenic and vacuum technology, and aspects of mechanical design. He used advanced software
techniques, e.g. GRASP, to simulate the optical beam coupling, and computer aided drawing packages to
prepare his designs for manufacture.
In addition to technical design, Pawala also undertook the measurement of some of our high-frequency
heterodyne receiver components, i.e. harmonic frequency up-convertors. This required him to use a range

2. of advanced microwave and millimetre-wave test and measurement equipment to gather relevant data,
e.g. vector network and spectrum analysers, power meters, millimetre-wave sources, etc. He also used a
variety of software packages to perform data analysis, and to support the presentation of his findings.
Pawala worked diligently and effectively at all times, and I found him to be a very pleasant person to
work with. He is very motivated and shows an admirable desire to explore new areas of work. I’m very
pleased to be able to recommend him to you for a placement at the AAO. I am sure that he would gain a
very considerable amount from the experience.
Yours sincerely,
Prof. Brian Ellison
Head of Millimetre Wave Technology Group and
ALMA UK Project Manager
This information is supplied in good faith and with no admission of liability to the STFC or RAL.