Vice Head of School, FFA
As professor of physics with specialisation in astroparticle physics, I develop instrumentation and methods which enable the study of the cosmic radiation from space platforms. My current research interest (2004-) is X-ray polarimetry - a new observation method allowing celestial sources to be studied in a systematically different way to contemporary approaches based on imaging, timing and spectroscopy. Prior to this (1999-2016), I worked in cosmic-ray physics (PAMELA mission) with a focus on using antiparticles as a probe of potential primary sources such as dark matter particle annihilations. In the distant past (1996-2001), I developed radiation tolerant opto-electronic solutions for the ATLAS experiment at CERN. My Ph.D. Thesis (University of Birmingham, 1996) concerned studies of b-quark hadrons using data from the OPAL experiment at the CERN LEP accelerator.
From January 2020, I am Deputy Dean of the Faculty of Engineering Sciences at KTH, and, 2012-2019, I was Head of the KTH Physics Department.
In recent years, I have been pursuing the development of novel instrumentation to study the emission of polarised hard X-rays (~10-100 keV) from the Crab - a pulsar and associated wind nebula in the constellation of Taurus, 6500 light years from Earth, and Cygnus X-1, a black hole binary system. Measurements are made using a unique telescope, built by my group at KTH, and flown on-board stratospheric balloons from the Esrange Space Center in Northern Sweden. The balloon mission, known as PoGO+, was successfully flown in summer 2016 from Esrange, and is described in this film. Take a look at my publications list for the scientific results from this flight.
Following on from the sucess of PoGO+, I led the development of a gamma-ray burst polarimeter, SPHiNX, for the Swedish National Space Agency "InnoSat" small satellite platform. The mission was studied to Phase A (2017), but was not selected for implementation. Maybe will try again some day... Again, see the publications list for further details.
In order to achieve an order of magnitude improvement in signal-to-background ratio compared to PoGO+, allowing a wider range of celestial objects to be studied, my research group joined the X-Calibur Collaboration in 2018. X-Calibur is also a balloon-borne hard X-ray polarimeter, but, unlike PoGO+, uses focussing X-ray optics with a resulting improvement in sensitivity. Observations of the accreting neutron star GX301-2 were made during a test balloon flight from Antarctica in December 2018. An upgraded mission, XL-Calibur, flew from the Esrange Space Centre in northern Sweden in summer 2022. My group prepared the new anticoincidence shield for the mission. The in-flight performance of the shield followed design expectations (see publications list), with a veto threshold of <100 keV and a polarimeter background rate of 0.5 Hz (20–40 keV). This is compatible with the scientific goals of the mission, where %-level minimum detectable polarisation is sought for a Hz-level source rate. The next flight of XL-Calibur is scheduled for summer 2024, also from Esrange. In the future, we aim to conduct a flight from McMurdo base on Antarctica for the study of high-energy sources on the southern sky.