One Dimensional Beam Position Monitor Prototype Using Incoherent Cherenkov
Diffraction Radiation
A. Clapp, Royal Holloway University of London, Egham, UKalso at Diamond Light Source, Didcot, UK
P. Karataev, Royal Holloway University of London, Egham, UK
L. Bobb, G. Cook, Diamond Light Source, Didcot, UKABSTRACTThis paper proposes a novel advancement in both the studies of Cherenkov diffraction radiation (ChDR) and beam instrumentation. The proposed beam position monitor (BPM) consists of two
identical fused Silica prism radiators, with a fibre collimator attached to each one, which in turn are connected to a photodetector via a series of optical fibres. The setup will be implemented into
the booster to storage ring transfer line at Diamond Light Source - an electron light source with 3 GeV beam energy. The prototype proposed aims to test the feasibility of a full BPM utilising
ChDR. If proven to be fully realisable, optical rather than capacitive BPM pickups could be more widely distributed. The paper will include the complete design and preliminary results of a onedimensional BPM, utilising the ChDR effect.
INTENSITY SIMULATIONSBOOSTER TO STORAGE (BTS) TEST STAND

Figure 2: Intensity simulation using equation 16 from [1]Figure 1: BTS test stand at Diamond Light Source (DLS) wherethe ChDR BPM is positioned.
Optical Transition Radiation (OTR) screens, Yttrium Aluminium
Garnet (YAG) and Inductive Beam Position Monitor (IBPM) inBTS are used for reference beam profiles and beam position
respectively.

Simulations performed for fused Silica targets shown in Figure 6, with DLS beam energy of 3 GeV for 500nm ChDRemission. The pick-ups have a vertical size of 32 mm, which as this is greater than 10 𝛾𝜆, the decay is predicted tobe exponential.

BPM ASSEMBLY

Figure 4: Showing 3D rendering of ChDR BPM assemblywith indication of beam direction.

Figure 3: Decay simulation of two identical targets
either side of a beam

FUSED SILICA PRISM

Figure 5: Picture of one pick-up ChDR
BPM assembly

As the beam passes through the gap between the two prisms, ChDR is emitted and collected via the twocollimators. For initial experimentation, only one side of the assembly is inserted into the BTS.

Figure 6: Showing 2D rendering of the ChDR target with beam
direction and ChDR emission.
The prisms have output faces angled at 90 − 𝜃!" to ensure
the emission wavefront is parallel to the output face, as
indicated by the cyan ChDR arrow.

PRELIMINARY RESULTS USING ONE CHDR PICK-UP
The one pick-up ChDR BPM assembly has been installed and commissioning is underway. Figure 7 shows the beam profileon the YAG screen located at OTR 2 (see Fig. 1), shadowed by the ChDR pick-up. Confirming that an impact parameter ofzero can be achieved between the electron beam and the pick-up. Figure 8 shows the corresponding output signals from theIBPM and the ChDR detector. The shadowing of the electron beam by the pick-up means this detected signal will be acombination of Cherenkov radiation and ChDR. This confirms that radiation emitted at the Cherenkov angle is successfully
captured by the collimators and transmitted through the fibre system

CONCLUSION
In conclusion a 1D BPM utilising incoherent ChDR has
been designed and characterised in the lab. The
assembly has been installed with one pick-up in placeon the BTS transfer line at DLS. Initial commissioning
tests have been performed and first signals have been
detected.

ACKNOWLEDGEMENTS
The authors would like to thank the efforts of theengineers at RHUL for creating the stainless-steel
assembly and the help of the DLS vacuum group withinstalling the ChDR assembly into the BTS.
Figure 7: YAG image of the beam profile being
shadowed by the ChDR assembly.

Figure 8:Detected output signal of the three IBPM
connections and the ChDR detector. Voltage divisions of 50mV and 0.5 V for the IBPM and ChDR signals, respectively.

REFERENCES[1] M. Shevelev and A. S. Konkov, “Peculiarities of the generation of Vavilov-Cherenkov radiation induced by a charged

particle moving past a dielectric target,” Journal of Experimental and Theoretical Physics, vol. 118, no. 4, pp. 501–511, Apr.
2014, doi: https://doi.org/10.1134/s1063776114030182.