NTA-HCCC

Stato aggiornato della sperimentazione

Vincenzo Guidi

Sezioni di FE, LNL, MIB (Como e TS)

Partecipazione esperimento UA9– CERNCoordinato da W. Scandale

2

5

3

1

4

6

Outlook

Sample preparation

Runs with negative charges (H4)

Runs with positive charges (H8)

Connection with UA9 experiment

Activity under way in 2009

Demand for lower roughness

An application of crystals would be the collimation of beam halo in next generation of hadron machines (e.g. the LHC)

Particles in the halo drift outwards at the rate of ~2 nm per turn. Since the tune is not integer, the particles will hit the crystal every ~10-20 turns and thereby the first impact parameter of the particles onto the crystal will be in the range of ~100 nm (curtesy of V. Previtali and R. Assmann)

It demands a crystal with a roughness lower than 100 nm on the lateral faces of the crystal

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 Negligeable

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

Photolythography

a) Starting material: (110) silicon wafer

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

Structural characterization

Lateral surface (AFM)

Sub-nm roughness was achieved

Entry surface (HRTEM)

High-quality surfaces achieved via ACE

Sub-nm roughness was

achieved

Previous runs

August and September data acquisition setup for 400 GeV/c protons and 150 GeV/c µ-, π- , K-

1.92x1.92 cm2 telescopes with reading steps 50 µm

Spatial resolution:5 µm

DAQ rate = 2.1 kHz

Goniometer

Perpendicular planes orientation(to looking for axial channeling)

Stage rotativo “culla”

goniometer

crystal

Vertical direction

Bended planes orientations(to looking for planar channeling)

Axial channeling

First observation of axial channeling with high efficiency.

Capability to divert 90% of beam particles towards an ordered direction

Negative particles I

First observation of:• planar channeling

• volume reflectionwith negative particles

Negative particles II

First observation of axial channeling with negative particles in a single strip

P(θx>0)=90.6%

MST14 Multistrips I

• 12 crystals aligned in ~400µm

• ~40µm volume reflection region with:

-no channeling-109µrad deflection angle

New crystal holder conception

MST14 Multistrips II

• 12 crystals aligned in ~100µm

• ~160µm volume reflection region with:

-no channeling-109µrad deflection angle

Different mass charge distribution over strips

MST14 Multistrips III

Volume Reflection

• Deflection angle:

109 µrad

• Efficiency:

94%Surprisingly

high level

MVR 2007 vs 2008

2007 2008

MVR 2007 vs 2008

Deflection angle: 40.5 radEfficiency: 93%

Deflection angle: 109 radEfficiency: 94%

MST curvature dependence

Volume Reflection:Deflection Angle VS Radius

Channeling:Efficiency VS Radius

MST15 Multistrips I

• Low efficiency channeling peak

• ~400 µm volume-50µrad deflection angle

Changed bending angle

MST15 Multistrips II

• No channeling peak

• ~750 µm volume-25µrad deflection angle

Changed bending angle

Multiple volume reflection in a single crystal

Volume reflection from different planes

Clear observation of multiple volume reflection in single strip crystal (V. Tikhomirov, PLB 655, 5-6, 2007)

Schemes for beam collimation

Planar channeling (ST9 for UA9)

Volume reflection (MST14 for UA9)

Axial channeling

Multiple volume reflection in a single crystal

The steering committee of the UA9 selected two crystals fabricated by

INFN

Scientific production

NIM B 249 (2006) 302

PRL 97 (2006) 144801

NIM B 252 (2006) 11

APL 90 (2007) 114107

APL 91 (2007) 061908

PRL 98 (2007) 154801

PLB 658 (2008) 109

RSI 79 (2008) 023303

PR ST 11 (2008) 063501

JPD 41 (2008) 245501

PRL 101 (2008) 164801

PRL 101 (2008) 234801

PRL 102 (2009) to appear

PRA 79 (2009) to appear

PRL 102 (2009) to appear

2009 Activity I

External line H410 days

Negative particles (µ- and π-) beam 150 GeV/c

Electron beam 150 GeV/c

External line H838 days

Proton beam 400 GeV/c

2009 Activity II

Planned experimental activity on H8

1. Investigation on multiple volume reflection

2. Observation of multichanneling (with piezo-systems)

3. New material (Tungsten)

4. New concept: silicon lens for channeling experiment

5. Observation of PXR with 400 GeV protons

2009 Activity III

Planned experimental activity on H4

1.Precise measurements of dechanneling length

2.Study of multiple volume reflection with negative charges.

Super-acceptance channeling I

With a silicon lens it is possibile to reduce the number of dechanneled particles by focusing the proton beam onto the center of the potential well, with a precise cut in the crystal

beam

cut

crystalz1

z2

z3

0

x

y z

Super-acceptance channeling II

Simulation of particle trajectories

Silicon crystal Silicon Lens

Super-acceptance channeling III

Channeling with focusing results in 99% efficiency!

0,0 0,2 0,4 0,6 0,8 1,00

5

10

15

20

25

30

θ

Pdech

, %

rms, μrad

7 TeV

0 1 2 3 4 5 6 70

5

10

15

20

25

30

35

40

θ

Pdech

, %

rms, μrad

400 GeV

,1

,71

,17

3

2

1

cmz

mz

mz

===

μμ

,1

,14

,4

3

2

1

mmz

mz

mz

===

μμ

Super-acceptance channeling IV

Implementation of the method of the cut through a buried SIMOX layer

Richiesta di integrazione

ME Inv

FE 4.5 16

LNL 2

MIB 4.5