Review of recently achieved measurements on crystals

Andrea Mazzolari

CERN, 10 Nov 2009

University of Ferrara and INFN - Italy

UA9 Collaboration meeting

Outlook

• Crystal fabrication• Crystal characterization• Torsion removal• H8 Crystals for SPS• H8 New materials and technologies• H8 Crystals for H4

• H4 axial channeling• H4 MVR in a single crystal

• Conclusions

Anisotropic etching I

Anistropic etching is a feasible way to realize sub-surface damage free crystals entirely by wet chemical methods

(100) (110) (111)

7.1 m/h 10.7 m/h Negligible

Etch rate on different silicon planes for KOH 20% at 40 °C

Photolithography

a) Starting material: (110) silicon wafer, off-axis: 120 μrad

b) LPCVD deposition of silicon nitride thin layer

c) Silicon nitride patterning

d) Etching of Si in KOH solution, silicon nitride acts as masking layer

e) Silicon strips release

f) Removal of silicon nitride

Fabrication of multistrips

Fabrication of either a multistrip or a batch of strips is possible through wet chemical methods

JPD 41, 24 (2008)

Characterization

Lateral surface (AFM)

Sub-nm roughness was achieved

Entry surface (HRTEM)

High-quality surfaces achieved via ACE

Sub-nm roughness was achieved

<111>

On-beam characterization

R = 2.4 m R = 4.5 m

R = 8.6 m

R = 38 m

ST9 crystal was characterized with 400 GeV protons in the external line H8 and installed in SPS ring

Planar channeling efficiency is very high

On-beam characterization

Single-pass efficiency of planar channeling exceeds 75% and 85% with quasi-parallel particles

On-beam characterization

Dependence of VR defection angle and its spread vs. crystal curvature

Comparison with theoretical model

PRL 101, 234801 (2008) V. Maisheev Phys. Rev. ST Accel. Beams 10 (2007) 084701

Torsion removal

Torsion removal II

Torsion removal III

H8 – ST 16 for SPS•Thickness: 2 mm•Ch planes: (110), mis-cut: -1500±20 urad•Bending angle: 150 urad,•Ch efficency: about 80%•Torsion: about 1urad/mm

H8 – ST18 for SPS•Thickness: 2 mm•Ch planes: (110), mis-cut: -200±20 urad•Bending angle: 176 urad,•Ch efficency: about 80%•Torsion: about 0.6urad/mm

H8 – QM1 for SPS•Thickness: 0.93 mm•Ch planes: (111), miscut: <300 urad•Bending angle: 130 urad•Ch efficency: to be analyzed•Torsion: to be analyzed

H8 – QM24 for SPS•Thickness: 4.0 mm•Ch planes: (111), miscut: 90 urad•Bending angle: 120 urad•Ch efficency: to be analyzed•Torsion: 5.3 urad/mm

-150 -100 -50 0 50 100 1501

10

100

1000

10000

Inte

nsi

ty (

a.u

)

Tilt (urad)

FWHM = 110 urad

H8 – Si-Ge crystal•Graded Si-Ge crystal•Ch planes: (111)

H8 – Si-Ge crystal•Thickness: 4mm along the beam•Ch planes: (111)•Bending angle: 176 urad

•Ch efficency: about 45%•θVR=12.8 urad•Torsion: torsion free

H8 – QM-Ge crystal•Thickness: 0.5mm•Ch planes: (111)•Bending angle: 200 urad•Ch efficency: to be analyzed•Torsion: to be analyzed

H8 – Lithium Niobate•Thickness: 1mm•Ch planes: (01-10)•Bending angle: 195 urad

•Ch efficency: about 3%•θVR=13 urad•VR efficency: about 90%

H8 – Multistrips•Thickness: 2 mm, 4 strips•Ch planes: (111)•Ch axis: <110>

•Bending angle: about 300 urad•θVR= about 44 urad•θVROC= about 150 urad

H8 – Grooved crystal•Thickness: 1.5 mm, 5 strips•Ch planes: (111)

•θVR= about 40 urad•VR efficicency: to be analyzed

H8 – Preparation of stripfor MVR on H4 I

•Thickness: 4 mm•Ch planes: (110)•Bending angle: 738 urad•Ch efficency: about 27%•Torsion: about 2.6urad/mm

H8 – Preparation of strip for MVR on H4 II

•Thickness: 2 mm•Ch planes: (110)•Bending angle: 670 urad,•Ch efficency: about 31%•Torsion: about 4.3urad/mm

H8 – Preparation of strip for axial ch on H4 I

•Thickness: 8 mm•Ch planes: (110)•Bending angle: 178 urad•Ch efficency: about 55%•Torsion: about 4.6urad/mm

H8 – Preparation of strip for axial ch on H4 II

•Thickness: 2 mm along the beam•Ch planes: (110)•Bending angle: 105 urad,•Ch efficency: about 65%•Torsion: about 1.8urad/mm

H4 – Axial channeling I•Thickness: 2mm•Ch planes: (110), ch axis: <111>•Bending angle: 105 urad

H4 – Skew planes

Main plane

Skew plane

H4 – MVR in a single crystal IUnder proper axial alignement VR from main and skew planes collapse in MVR in a single crystal

H4 – MVR in a single crystal II•Thickness: 2mm•Ch planes: (110), ch axis: <111>•Bending angle: 738 urad•MVR deflection angle: about 60 urad

First observation of MVR in a single crystal with negative particles

Conclusions•Established a reproducible method to remove torsion in strip crystals

•Two strip crystals fully characterized and ready for installation in SPS

•Started researches on channeling and VR with new materials and technologies

•First observation of MVR in a single crystal with negative particles

•Succeffully observed planar and axial deflection of negative particles at large bending angles