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 12/05/2018

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, 12/05/2018

Micro-EBS on the diamond before irradiation Si + Diamond Diamond Diamond range: 200 – 350 [ch] Only Si

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 12/05/2018

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 ) 12/05/2018

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) 12/05/2018

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 12/05/2018

Thermal and electrical properties of graphite, diamond and silicon Thermal conductivity [W/mK] 119 - 165 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 12/05/2018

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