Fabrication of strip-like crystals for channeling CC-2007 -  CARE-HHH-APD mini-Workshop on Crystal Channeling for Large Colliders: Machine and Physics Applications Fabrication of strip-like crystals for channeling Vincenzo Guidi on behalf of the Sensors and Semiconductors group at University of Ferrara and INFN CERN, March 22nd 2007

Outline Preparation of Si strip-like crystals (2006) Preparation of Ge strip-like crystals (2007) Preparation of thin Si strip-like crystals (2007) Investigation on complex crystals (2007) Configurations for multiple volume reflection (2007)

Silicon strip: fabrication Samples are fabricated by dicing of a high-quality Si wafers Miscut angle < 0,5 mrad TTV < 3 m Dimensions (mm) W L H 70 2 0.2 0.5 0.9 1 3 (111) orientation (110) orientation

RBS-channeling spectra Chemical etching Isotropic wet-chemical etching planar etching HF + HNO3 + CH3COOH etching = about 2 m after chemical etching before chemical etching RBS-channeling spectra

Bending of the strip Deflection is provided by anticlastic forces though externally imparted mechanical forces At H8-SPS bending angle was fixed at about 150 μrad

Observation of volume reflection beam Successful observation of VR with strip-like crystals with (110) orientation crystals sizes: 0.9 x 70 x 3 mm3

Germanium: sample fabrication Miscut angle < 0,5 mrad TTV < 3 m Dimensions (mm) W L H 70 2 0.5 Samples with (111) and (110) orientation Reconsideration of chemical etching due to different reactivity of Germanium vs. Silicon

Germanium: characterization Characterization of the samples via RBS-channeling (courtesy of A. Vomiero) Samples delivered to IHEP for experiments with 70 GeV protons and available for the H8 RD22 runs

Germanium: bending Courtesy of D. Vincenzi Interferometric measurements made with a Zygo Fizeau-type interferometer strip Wafer orientation: (110) Strip size: 2x0.2x70 mm3 Main radius of curvature: -631 mm Anticlastic radius of curvature 3764.4 mm Deflection angle: 500 µrad

Thin strips I New fabrication methodology to prepare thin strips (achieved by both fully chemical and mechanical methods) Dimensions (mm) W L H 70 0.2

Thin strips II Recent observation of channeling with 450 MeV positrons at the BTF at LNF Ideal crystal for extraction in machines for adrotherapy Peak of channeling Courtesy of M. Prest

Investigation on complex crystals I Natural and artificial zeolites offer high acceptance for channeling Calculation of potential and electric field in zeolites (courtesy of V.A. Maisheev)

Investigation on complex crystals II Ca Reduced backscattering yield in channeled beam geometry in old sample 2 cm Direction of channels New samples ready to be prepared and characterized with RBS channeling

Configuration for multiple volume reflection Ideally a series of strips would multiply the reflection at each individual strip θref θacc At 400 GeV it holds: A series of parallel strips appears to be affordable

Configuration for multiple volume reflection Ideally a series of strips would multiply the reflection at each individual strip θref θacc At 400 GeV it holds: A series of parallel strips appears to be affordable How to do it?

Silicon multi-strip Fabrication of a preliminary sample of a multi-strip with (111) silicon by mechanical dicing Technology to achieve multi-strips through fully chemical methods (110)

Silicon multi-strip Fabrication of a preliminary sample of a multi-strip with (111) silicon by mechanical dicing Technology to achieve multi-strips through fully chemical methods (110)

Undulator I θref θref

Undulator I θref An undulator would be a compact “multi-strip” with millimetric or sub-millimetric period θref Technology developed in a previous study θref 200-2000 μm PRL 90 (2003) 034801 Easy to compensate for the shift of the tangency point with a global curvature (non-parallel configuration)

Undulator II The method of grooves proved the possibility to implement a crystalline undulator with proper parameters Courtesy of Y. Ivanov Sample produced in Ferrara The bending of crystal from one groove is ~80 rad for grain size 40-60 m and ~20 rad for grain size 4-6 m with 300 m samples

Undulator III Alternative method to generate a periodic structure within a crystal: deposition of an alternate tensile coating It allows exploitation of the full cross section of the crystal featuring quasi-sinusoidal deformation field

Undulator III Alternative method to generate a periodic structure within a crystal: deposition of an alternate tensile coating It allows exploitation of the full cross section of the crystal featuring quasi-sinusoidal deformation field APL 90 (2007) 114107

Conclusions Production of Ge samples for H8 Optical characterization of curvature Investigation on zeolites Production of thin Si crystal Realization of a Si multi-strip Undulator as a multi-strip