1. Progress report on the internal target
F. Iazzi (Politecnico), V. Rigato (LNL) and
H. Younis (Politecnico)
Radiation damage: proton irradiation of the diamond disk
EBS test on the irradiated diamond disk
Raman spectroscopy on the (not irradiated) wire
Conclusions
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2. Production of the Internal Target by Diamond disk
Starting from: Disk shaped diamond
Obtained by Chemical Vapour Deposition on a circular Si ring.
Features:
High Thermal conductivity
High Mechanical Resistance
Low electric conductivity  stripping problems
Diamond disk thickness 3±0.5 mm thick and 99.9% pure provided by the factory.
Surfaces : Polished (but slightly Wavy)
Si(Silicon) Ring:
Inner diameter f=11mm,
Outer diameter f=15mm,
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3. Micro-EBS on the diamond before irradiation
Si + Diamond
Diamond
Diamond range: 200 – 350 [ch]
Only Si

4. Preliminary tests for radiation damage
Diamond disk irradiated in two points and same back scattering test was applied. P1 P2
Used Beam: proton
Proton Energy : 1.5 MeV
Proton current: 480 pA
Spot size A1=3470*3470 mm2
Irradiation Time T1 ≈ 1 hour
8.3 x 1013 p/cm2
Spot size A2=870*870 mm2
Irradiation Time T2 ≈ 2 hours
3.1 x 1015 p/cm2
P1: point where diamond disk was irradiated toward the periphery
P2 : point where diamond disk was irradiated nearly at its centre
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5. Back Scattering on Diamond after irradiation
Back Scattering test on 2 points of the central region of the disk (pure diamond)
Simulation (continuous line) and experimental data (red dots) show a very good agreement
Results:
Tests on both irradiated points show a homogeneous composition and thickness, similar to the virgin specimen
Presence of :
12C(99.9%)
No 16O and H contamination was observed
Areal Density r = 50.2x1018 atm/cm2 (greater than graphite, 34x1018 atm/cm2 )
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6. Test on the wire: no irradiation, Raman on virgin sample
Thin wire obtained by cutting diamond using LASER
Wire width = 99.9±0.5 [mm]
The wire have been submitted to Raman Spectroscopy in-order to check the effects of the LASER cut on the internal structure
3 regions have been examined along the width of the wire: border (region of the LASER cut),
center of the wire,
periphery (region between border and center)
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7. Raman Spectroscopy on the wire
Bottom Curve (Wire centre): shows only a clear peak in the D (diamond) phase.
Middle curve (Wire periphery) shows a very slight enhancement in the region of Graphite (G Band)
Top curve (Wire border): shows a dominance of Graphite phase vs Diamond Phase .
Top curve; shows a dominance of G phase w.r.t D one. Bottom Curve; shows only a clear peak in the D (diamond) phase.; Middle curve; shows a very slight enhancement in the region of Graphite (G Band).
Conclusion: after LASER cut, 2 lateral strips of graphite appear on the target, while the central region remains diamond
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8. Thermal and electrical properties of graphite, diamond and silicon
Thermal conductivity [W/mK]
2300
149
Electric conductivity [1/W m]
108
10-16
Expected properties of the internal target:
Good thermal conductivity to dissipate released heat from beam: central region
Good electric conductivity to neutralize the electrostatic charges (stripping): border
The Si ring is thermal but not electric conductor: new connections with the beam pipe must be studied
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9. Conclusions & Future work
The diamond CVD material shows a higher density than graphite
After irradiation, the structure of CVD diamond doesn’t seem damaged: properties remain the same as virgin
The Si ring is pure Si in the border, somewhat overlapped by diamond close to the internal radius
The effect of the LASER cut on the wire sides is creation of 2 lateral strips of highly (electrical) conducting graphite which could ensure the electron refill against stripping
Produced heat could be dissipated by the central region
The Si ring is an insulator: a contact with a conducting material should be designed
Future activity will concern:
Irradiation of the wire with proton of equivalent energy deposit
Tests of the same type (EBS + Raman) on the irradiated regions
Study of the contacts diamond-conductors
Cutting new targets (bigger? What diameter?) (with our own LASER)
Measurements of the electric and thermal conduction of the wire(!)
PS: these results presented by H.Y. at INTDS (Mainz, August), published in Journal of Radio Analytical and Nuclear Chemistry and re-presented at Barcelona PostGrad Encounters on Fundamental Physics
12/05/2018