Laser and Beam Diagnostics Tools for the L

Laser and Beam Diagnostics Tools for the L 3 IA facility at Pisa Dario Giove on behalf of the L 3 IA collaboration 3 rd ELIMED Workshop LNS 7 -10 September 2016

L 3 IA • Motivation of the proposal • Status Detectors and setup-tools • Optical tools for laser beam setup • Diagnostics for the proton beam Optical Tools • Rear electrons OTR • Optical spectroscopy as a pre-plasma diagnostic Current, energy and transverse size diagnostics • Noise considerations • EBT 3, CR 39, solid state diodes • Diamond based TOF • Integrating Current Transformer • Rad. EYE (CMOS matrix detector) • Fast Faraday Cup (FFC) 1 3 rd ELIMED Workshop LNS 7 -10 September 2016

The main goal of L 3 IA project is to establish an outstanding beam-line operation of a laser- plasma source in Italy. In particular, our goal is to investigate the laser-driven ion acceleration with the Target Normal Sheath Acceleration (TNSA) mechanism. L 3 IA will be ready to operate at the ILIL installation in Pisa at a first laser driver power of 100 TW in the first half of 2017, focusing on the identification of the laser -target interaction and the acceleration regime suitable for a reliable operation of the test facility. 2 3 rd ELIMED Workshop LNS 7 -10 September 2016

Final L 3 IA beamline L 3 IA preliminary activity (@10 TW) ILIL current st L 3 IA@ILIL 1 phase L 3 IA@ILIL final ph 3 3 rd ELIMED Workshop – LNS 7 -10 september 2016

According to the project schedule, preliminary L 3 IA experimental runs started in 2016 with the existing 10 TW system, dedicated to: - optimization of focusing and target control - identification of the interaction regime - Thomson-parabola measurements - solid state detectors development - RCF and CR 39 measurements, TOF measurements Multiple diagnostics were set up of the laser-plasma interaction (specular reflection spectroscopy), the fast electron production and transport (X-ray spectroscopy, OTR emission), the proton acceleration (magnetic spectrometer, Thomson parabola, TOF diagnostic, . . . ) 4 3 rd ELIMED Workshop – LNS 7 -10 september 2016

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Optical spectroscopy as a pre-plasma diagnostic Observation of integer and half-integer laser emission from the front side provides infos on the preplasma 2 w. L emission => interaction at the critical density layer& 3/2 w. L - two-plasmon decay from underdense plasma &L. A. Gizzi 6 et al. , Phys. Rev. Lett. 76 , 2278 (1996) 3 rd ELIMED Workshop – LNS 7 -10 september 2016

The experimental measurements show an onset of the 3/2 w. L harmonic close to around 3 Rayleigh lengths around the best focal position This results are in good agreement with the estimates made using the plasma scalelength at nc/4 as retrieved by hydrodynamic simulations of the target expansion after the intaraction with the laser (pre)pulse profile. According to these simulations, target thicknesses down to around 2 -3µm can be considered for TNSA experiments, while care has to be taken for thinner targets Data taken using an Ocean Optics integrated spectrometer model USB 4000 7 3 rd ELIMED Workshop – LNS 7 -10 september 2016

OTR imaging at the rear side of the target Fast electrons crossing the rear solid targetvacuum interface gives rise to Optical Transition Radiation, which can be used as a diagnostic of fast electron spectrum (under certain hypotheses), energy spectrum, duration and so on, and fast electron transport We have carried out extensive OTR rear imaging, which showed a strong coherent OTR emission Well localized optical emission Correlation with fast electron emission Polarization analysis consistent with OTR Shape of emission reproducible from shot to shot Similar emission found for Al, Cu and mylar 8 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Laser Shot and Particle Emission Induced Noise • Background em pick up noise along signal cables (length up to 30 m): +/- 50 m. Vp, 5 MHz • Em noise induced after the laser shot on the target, lasting hundreds of ns +/-1 Vp, 250 -350 MHz with reflections due to impedance mismatch 9 3 rd ELIMED Workshop – LNS 7 -10 september 2016

In june 2016 we made some significant improvements: All the internal cables were substituted using a new shielded Coaxial Cable named SPUMA_240 -FR-01 A new electrical line devoted to grounding and shielding of signal paths was installed with a direct connection to the bulding main transformer reference. The target holder was referenced to this ground along with the whole chamber Results: Shooting the laser on a glass target we had a reduced noise of +/- 15 m. Vp on a diamond detector Shooting the laser on an aluminium target we had an overall noise of +/- 200 m. Vp on a diamond detector All the measurements were carried out using a large bandwidth electronic setup 10 3 rd ELIMED Workshop – LNS 7 -10 september 2016

PISA @Dicembre 2014 EBT 3 with polyetilene removed 11 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Silicon diode arrays Develop a position sensitive silicon detector according to a matrix scheme based on simple PIN diodes Advantages of a Si-PINarray over a MCP+CCD detector: • The Si-PINarray operate without any requirement about high and clean vacuum conditions • The Si-PINarray is cheaper and simpler • The Si-PINarray is much more robust and reliable • The Si-PINarray solution allows to design detector geometries according to the specific requirements of the experiment (i. e. parabola shapes of the ion trajectories after a TP) 12 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Different possible sources for Si-PINArrays: • Custom designs • Micron Semiconductor • Hamamatsu For the first tests we chose to start with Hamamatsu products (although Hamamatsu does not provide any information about the geometry of the detector in term of the PN junction thickness). The commercially available packages provides up to 46 elements (model S 4114 -46 N) or a basic architecture which will allow to grow simply stacking more packages (S 5668 -021/SPL) The active area of each element is of the order of 1. 5 x 0. 9 mm 13 3 rd ELIMED Workshop – LNS 7 -10 september 2016

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Diode discrete detector (16 points of measure at a step of nearly 1 mm each) The detector is aimed to be used as a low cost solution for monitoring purposes (size and position of the emitted protons) Placed after a simple permanent magnet deflection unit may be used as a simple and low cost energy identifier. LOA @December 2013 16 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Diamond based TOF measurements (300 mm length of flight) end of june 2016 0. 7 Tesla permanent magnet inserted to remove unwanted electrons 17 3 rd ELIMED Workshop – LNS 7 -10 september 2016 500 micron thickness diamond collimator bore diameter 2 mm

Measurements carried out in 2015 and first months of 2016 18 3 rd ELIMED Workshop – LNS 7 -10 september 2016

The prompt peak seems dominated (!) by electrons with a small contributions from X rays (and perhaps secondary electrons Excellent noise figure: less than +/- 100 m. Vp 19 3 rd ELIMED Workshop – LNS 7 -10 september 2016

In the near future … We will use thin diamond detector (less than 200 um). We will have samples of about 50 um thick and with a charge collection distance of >10 um, with a S/N ratio of 5 or more. We will use a new Data Acquisition System based on a NI PXIexpress chassis which will be installed close to the target chamber and driven through an Ethernet line. A client panel has been developed to run on remote computers. The ADC section will foresee 2 channels each one able to work @ 1. 5 GHz bandwidth with a 5 GS/s sampling rate. 10 bit resolution characterize the vertical resolution. 20 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Fast Faraday Cup A fast faraday cup, with a 2 GHz bandwidth, has been developed and tested. Pulsed beams with FWHM of the order of 500 -700 ps have been measured. It may be a very nice and simple tool to be used in TOF experiments. We will test the sensitivity in the specific environment. 21 3 rd ELIMED Workshop – LNS 7 -10 september 2016

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Bergoz Integrating Current Transformer ICT combines two nested transformers: A shorted one-turn current transformer loads the full bunch charge instantly into capacitors. Then the charge is transferred to the output by a readout transformer, at a slow pace, to avoid core loss. Cores are specially annealed to lower their coercive field and further minimize core loss. The ICT signal is integrated by BCM-IHR, a boxcar-type differential amplifier. The output voltage proportional to the beam pulse is available 30 μs after the trigger. It is maintained up to 400μs (adjustable), then reset. Another pulse can then be measured. 23 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Test bench measurements of the detector performances The graph shows the results of the test bench measurements: T 2 is the output of the ICT as a current pulse charged on 50 Ohm and large BW amplified (1500 MHz with 40 d. B gain) due to a single pulse of beam charge of 1 p. C; TB is the averaged of T 2 after 1000 samples output of the ICT The measured sensitivity of the detector is of 0. 2 p. Crms (1. 2 x 10^6 protons). 24 3 rd ELIMED Workshop – LNS 7 -10 september 2016

Development of a detector based on pixel solid state CMOS module for destructive diagnostics Large area detector: CMOS photodiodes array • • • 25 Detector size 25 x 50 mm Pixel size 48 micron 512 by 1024 matrix of silicon photodiodes Dinamic range 85 d. B Max. frame rate 4. 5 fps (extimated) effective active layer of 6 micron 3 rd ELIMED Workshop – LNS 7 -10 september 2016

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The detector has been qualified in lab tests for the shielding to high power light pulses and for the behavior during the interaction with alfa particles. The light power pulses (coming from a flash synchronized with the exposure timing signal of the detector and with a power of the order of 10 k. J) has been shielded in a very effective way using 24 micron thickness aluminum foil , reducing the contribution to the detector response down to the natural thermal contribution. 27 3 rd ELIMED Workshop – LNS 7 -10 september 2016

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Beam tests The Rad. Eye based device consists of a couple of modules. The first one (devoted to the electronics) is designed to operate in air close to the line where the second one (which houses a dedicated PCB with one or two sensors) is positioned usually under vacuum. To verify the performances of the device versus an accelerator delivered beam we had the possibility to run an experimental test at the LNS Catana facility. Measurements were carried out with a continuous primary proton beam of 10 n. A chopped by a mechanical valve with an open time of 50 ms (equiv. 3 x 109 pps). Reducing the beam current of a factor of 10 the detector still works with an acceptable S/N ratio (equiv. 3 x 108 pps). To assess the capability to recognize a contribution from protons with different energies a staircase shaped plastic phantom has been inserted in front of the detector. The pictures obtained clearly shows that the system is able to image the pattern of deposited energy. 29 3 rd ELIMED Workshop – LNS 7 -10 september 2016