A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 A Narrow Field Lobster Eye Telescope (for SVOM and similar) Dick Willingale Adrian Martindale, Jim Pearson, Charly Feldman, Julian Osborne University of Leicester

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Square Pore X-ray Optics Square micro-pore optics can be used in 2 geometries –Wolter Type I – like XMM-Newton, Chandra, Swift… –Lobster Eye – Angel plates, 2 reflections in plane 1 plate, 2 reflections perpendicular planes

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December Square Pore Micro-Channel Plates Glass plate full of holes! – thickness mm – transmission ~67% Square Pores L~1 mm, d~20 μm, wall~4 μm, L/d~50 Cartesian packed pores for Lobster Eye Radially packed pores for Wolter I

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Wolter I to Lobster Eye Bepicolumbo MIXS-T uses Wolter I geometry –The flight model has been made and works BUT –Very difficult to integrate and align –Requires 2 plates for every sector of aperture The narrow field lobster design for SVOM MXT –Much easier to integrate and align –Only requires 1 plate for each position in aperture 4

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Lobster Eye Optics Each pore splits the incident beam into 4 beams –0, 1, 1 or 2 reflections An array of pores on a spherical surface focus X-rays The field of view only limited by size of optic or detector 5

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Effective Aperture and PSF Distributions of flux from the array of pores –2 reflections from adjacent walls – focused spot –1 reflection – cross-arms –0 reflections – straight through –Multiple reflections from opposite walls Aperture circle radius F.d/L(2√2+1) 6 2 adjacent 1 0 N opposite

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Sources of Error in Lobster Eye Intrinsic to geometry L/d=50, d=40μm, F=1 m, E=1 keV –Spherical aberration Δθ s =4√2(d/L) 3 ~10 arc secs –Geometric pore size Δθ g =d/F ~10 arc secs –Diffraction Δθ d =2λ/d ~ 10 arc secs Intrinsic to plates –Bias error – pores not perpendicular to plate surface –Figure errors on the reflecting pore walls –X-ray scattering from surface roughness of pore walls –Alignment of pores – slumping errors –Pore shear errors 7

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Sources of Error – slumping + shear 8 Slumping errors/pore alignment Δθ a =2θ a ~0.75 arc mins Shear Δθ h =4√2(d/L)θ h Θ h =20 arc mins, Δθ h =2.3 arc mins

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Sources of Error – surface roughness Surface roughness power spectrum –Integral  13Å rms -> 20% losses at 1 keV –Scattering angles -> ω b =350 mm -1 Currently available MCPs – sum of all intrinsic errors –Central spot FWHM ~4.4 arc mins 9

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Narrow Field Lobster Eye Telescope F=1150 mm Aperture 210x210 mm 2 10 Total mass of integrated optic ~1 kg (~250 kg/m 2 )

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Narrow Field Lobster Eye Optimization 11 Maximize area at 1 keV For wide field L/d≈50 constant For narrow field - maximum area on axis - L≈2.5dF/R F=1150 mm d=40 μm 21 square pore MCPs - each plate has aperture 38 x 38 mm 2 L 1.22 – 2.74 mm L/d

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Vignetting at 1 keV Optimized –On-axis ~32 cm 2 Fixed L/d=50 –Maximum ~21 cm 2 Field of View –Diameter ~6 degrees –Not as narrow field as Wolter I Grasp –~350 cm 2 deg 2 –Swift XRT 15.2 cm 2 deg 2 12

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Narrow Field Lobster Area vs. Energy 13 F=1150 mm Red Includes Filter+CCD detector

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Narrow Field Lobster Predicted PSF 14 Focusing gain ~1900 PSF – constant over FOV FWHM ~4.4 arc mins

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Breadboard Model X-ray Testing 15 Al support frame – spherical surface R=2000 mm Machining accuracy ±10 μm 2x 20 μm plates, 2x 40 μm plates, 1x Ir coated plate Testing 1 plate Leicester TTF Source at 27 m F=1000 mm

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Measured Imaging 1.5 keV 16 Single plate 5 plates Bias angle errors splits focused spot? 2 adjacent reflections - focus 1 reflection - cross arm 0 reflection - straight through

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Sensitivity to transients Black – Swift BAT GRBs Red – Swift BAT short GRBs Green – Swift GRB afterglows Solid –Low NH 3x10 20 cm -2 Dashed –High NH cm -2 17

A Narrow Field Lobster Eye Telescope Dick Willingale – AXRO December 2014 Position Accuracy For Transients R90 – radius which contains 90% measured positions Beam used has diameter 10 arc mins Typical GRB –R90 ~10 arc secs 18