Multiple Volume Reflection in a series of crystals

Multiple Volume Reflections in a Series of CrystalsUA9 collaboration meetingGeneva, 10 November 2009Vincenzo GuidiDepartment of Physics and INFNUniversity of Ferrara, ItalyMultistrip MST14

14 silicon strips

1 mm spacing

1 mm along the beam

0.3 mm thickness

bending radius 4.5 mCampaign of measurements in 2008 at external line H8

Data Analysis 2008:Channeling Peaks of 12 strips

Data Analysis 2008:Volume Reflection Region of 12 strips

Region without channeling peaks

Data Analysis:Amorphous region97.5% particles in 3 region; cut@10rad

Data Analysis:MVR region88.2% particles in 3 region; cut@10rad = 91.2%

Data Analysis:MVR region88.2% particles in 3 region = 91.2%Particles with negative deflection = 92.6%Difference between the two efficiency definitionsData Analysis: single strip parameters

PRL 101 (2008) 234801

Some observations

VRVRVRaccOn assuming the stochastic independence in performance of the strips, expected efficiency is about 0.98Nstrips= 0.9812~0.78. Measured efficiency was 0.92.

Volume reflection peak is broader than for a single crystal.

There is a small fraction of particlesprobably channeled particleswith a deflection angle less than the bending angle.

Maximum efficiency occurs at the end of volume reflection regionVolume Capture-Assisted Multiple Volume ReflectionNon channeled particles at the first crystal are volume-captured and emerge at the end of the first crystal

Due to some misalignment between the strips, volume-captured particle may be volume-reflected at the second crystal and be recycled in the mechanism of MVR

ref

>098%2%Volume Capture-Assisted Multiple Volume ReflectionReversing the sign of the angle between the strips does not allow re-capture of volume-captured particle at previous strip.

If such particle will not interact with other strips it results in deflection to an angle opposite as that of MVR

ref