Elliptically polarised soft X-rays produced using a local bump in MAX II characterisation of the degree of polarisation

• MAX-lab has introduced a local perturbation to the electron orbit of the MAX II storage ring, providing users at the SX700 monochromator beam line, D1011, with elliptically polarised soft X-rays. This is achieved by using corrector magnets to send the electron orbit on an ascending or descending trajectory through the dipole magnet source. This simple "bump" approach has many advantages over and above insertion device based solutions. To illustrate the potential of the approach, the degree of circular polarisation, Pc, has both been calculated and measured. The calculation was made by applying the Stokes formalism to the intensities given by the standard dipole emission formula. Experimentally Pc was characterised using X-ray magnetic circular dichroism measurements. In such experiments magnetic contrast scales directly proportional to Pc. Using a 25 atomic layer bcc Fe film deposited on the Cu(100) surface as a calibration standard the spin moment, ms, was determined. By comparing the values of ms obtained here with those reported earlier, the degree of circular polarisation could be estimated. At ~715 eV the calculated and measured values of Pc are 0.93 and 0.85, respectively

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

X-ray magnetic circular dichroism measurements

magnetic contrast

atomic layer bcc Fe film

Cu(100) surface

calibration standard

spin moment

dipole emission formula

Stokes formalism

circular polarisation degree

insertion device based solutions

dipole magnet source

corrector magnets

D1011

SX700 monochromator beam line

electron orbit

local perturbation

MAX II storage ring

local bump

elliptically polarised soft X-rays

soft X-rays production

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