Appendix B

Stand-alone manual for theRasCLiC set-up in TT1

The Transfer Tunnel One (TT1) at CERN, a tunnel where particle beamswere transferred from the Proton Synchrotron (PS) to the Intersecting Stor-age Rings (ISR) until about 1984 when the ISR was decommissioned, ishome to a 140m test set-up (see Figure B.1). This set-up was con-

Figure B.1: The used part of TT1 (in red) relative to underground structuresat CERN. At the South side of the LHC, the Super Proton Synchrotron(SPS) is just visible on this map

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Figure B.2: Schematic lay-out of the alignment systems in the TT1 set-up

structed to test several alignment systems on same scale as the overlappinglarge distance alignment of the CLiC is designed (about 200m). Today theWire Positioning System (WPS), Hydrostatic Level System (HLS), Tilt Me-ter System (TMS) and the so-called RasCLiC are read out along side eachother. The HLS and TMS give corrections to the WPS (e.g. for the wiresag) and the (double) RasCLiC is the NIKHEF-built Rasdif system for CLiCto complement these systems or to be compared to them. Explanations ofthe alignment systems at TT1 can be found in Chapter 2 of the thesis (vanHeijningen 2011) where this (stand-alone) manual is found in the appendix.

Figure B.3: Photograph of the laser side of the TT1 set-up. One can distin-guish a vacuum tube (red), the WPS (green) and the HLS (cyan)

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B.1 Lasers

The RasCLiC system is a double Rasdif over 140m, where the lasers areat the North-East section of the tunnel at the start of the bending to theEast. The two lasers were installed on 28 and 29 November 2011 and linkedto the vacuum tube by means of bellows. Bellows where used to ensureindependent movement of vacuum tube and the laser set-up.

Figure B.4: Technical drawing of the laser-mount (courtesy of R. Rosing)

The design of the laser-mount was done by R. Rosing (NIKHEF) and hasdimensions similar to the fibre out-couplers of the red HeNe lasers (MellesGriot 05LHR925 and 25LHR925) used until the summer of 2011. It has beentested to meet the standards for running in a vacuum around 10−4mbar atNIKHEF on the 25/11/2011. The technical drawings of the laser-mount isshown in Figure B.4. The laser (indicated in green) is glued into a circularplate and the direction of the laser beam can be altered by six bolts, whichattach the plate to the three threads. One can distinguish eight screws;the four metallic ones ensure tight fixing of the mount and with four darkones one can alter the direction of the laser beam when its enclosed in thevacuum. In the mount, the former 4 screws have a larger hole than theirthread, so that translation in the directions perpendicular to the set-up ispossible. An alteration was made during production to ensure access to alleight screws: the 45 ◦ angle of the tube on the side is now a 22.5 ◦ angle.

A photograph of the laser side with only one bellow installed is shown inFigure B.5. The laser type is Diode Pumped Laser Diode (DPSS) emittinggreen light at 532nm and has proven to have the desired characteristics forthis set-up. It has a large intensity for its size, can thus easily be made to

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Figure B.5: The two lasers of the RasCLiC, one linked to the vacuum tube

fit in a vacuum envelope, emits coherent (enough) light up to 140m, and thevirtual point of departure of the coherent light almost coincides with thephysical location of the crystal. The only drawback is that it consumes (anddissipates) a lot of power compared to its output (close to 350 mA at 3V,so 1.05W). When it was tested at NIKHEF one could feel a fair increase oftemperature of the messing cylinder, indicating the dissipation of electricalpower. Both lasers have their own Delta (δ) power supply to ensure stabilityduring operation. These δ power supplies have a maximum current outputof 600mA, so running both lasers on the same power supply would not work.When both lasers ran on just one power supply, the intensity of the laserswould variate substantially.

B.2 Vacuum tube and pumps

In Figure B.3 one see the North-East section of the vacuum tube: the laserside where the tunnel starts to bend to the East. The vacuum tube isa stainless steel tube with an inner diameter of 155mm. It is made upof sections of some 6m and these are connected by clamps. At the laserside of the tube, two smaller tubes of about 10cm are welded on. Thismakes installation of bellows to the individual lasers possible and makes itpossible for the lasers to be in vacuum as well. Half-way down the tubeflexible bellows are attached to ensure easy installation of the diffractionplate section. At the South-West side of the set-up (the camera side) thetube is sealed off with a perspex plate.

Inside the vacuum tube, several diaphragms are installed. Figure B.6shows one of these diaphragms of which, with variable size (larger diameter

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near the diffraction plate section), seven are located along the length of thevacuum tube. They have a ’shark-teeth’ shape to ensure that they do nothave a well-defined diameter, which counteracts unwanted diffraction. Thediaphragms were installed to get rid of interfering reflections in the vacuumtube that would fall om the diffraction plate or the camera.

Figure B.6: ’Shark-teeth’ diaphragms in the vacuum tube

(a) (b)

Figure B.7: (a) Pressure read-outs of the pumping stations and (b) the valveone can use for releasing the vacuum

Attached to the vacuum tube one can find three pumping groups. Andrede Saever (CERN vacuum) closed the vacuum tube on 29 November andstarted the pumping procedure. This has brought the pressure down to1.5·10−4mbar in about three days starting from atmospheric pressure at12:36. This is shown in Figure B.7(a) and Table B.1. Located on the centrepumping group is a valve to release the vacuum in a controlled way (seeFigure B.7(b)).

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Date Time Pressure readout [mbar])

29/11/2011 12:36 103

15:45 2.05

30/11/2011 11:45 5·10−4

01/12/2011 10:30 2·10−4

02/12/2011 11:20 1.5·10−4

Table B.1: Pressure read-outs by A. de Saever (CERN Vacuum)

B.3 Diffraction plate

In the middle of the set-up, a diffraction plate is placed to diffract theincoming light coming from the lasers. The plate contains two identicalpatterns now known to its users as ’the four sausages’. Below one can seethe design of one of those diffraction patterns (Figure B.8(a)), a simulateddiffraction pattern[116] (Figure B.8(b)), a photograph of the diffraction plateholder(Figure B.8(c)) and a photograph of the camera image read-out on thePC (Figure B.8(d)). By hanging weight via a pulley on the threads wherethe diffraction plate holder one can translate in the horizontal direction andby turning the six bolts one can translate in the vertical direction.

(a) (b)

(c) (d)

Figure B.8: (a) Design and dimensions of the diffraction pattern, (b) sim-ulations of the resulting diffraction pattern, (c) a photograph of the plateholder and (d) a photograph of the camera read-out at the PC

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Property or Feature Specification

Colour/BW BW cameraEffective picture elements 1004(H) x 1004(V)Picture size 1000(H) x 1000(V), all modesCell/Pixel size 7.4µm x 7.4µmResolution depth 8, 10, 12 14 16 bit (high SNR mode)Digital interface IEEE 1394b (S800); IIDC V1.31Transfer rate 100, 200, 400, 800 Mb/sADC 14 bitFrame rates Up to 48Hz (full resolution)Gain control Manual: 0-24 dB (steps of 0.0353 dB)Shutter speed 35µs - 67s; Auto shutterDimensions 44mm x 44mm x 90mmOperating temperature 5 ◦C - 55 ◦CPower consumtion 5W

Table B.2: Specifications of the PIKE F100B cameras

B.4 CCD cameras

The side where the read-out of the system takes place is the side where thecameras and the PC are. The camera-type is PIKE F100B Fiber from AlliedVision and its specifications are shown in Table B.2.

(a) (b)

Figure B.9: (a) Catalogue picture of a PIKE100B and (b) two PIKE F100Bcams in the TT1 set-up

The two cameras can be adjusted in height via the 8 bolts that canmove vertically on the thread. The horizontal direction of the complete twocamera structure is fixed as the plate with the threads is bolted to a metro-logical plate. If a horizontal translation is needed to have images on thecameras, which is not possible without dismounting the cameras from themetro-logical plate, one has to keep in mind that the horizontal location ofthe images can also be altered by translation of the diffraction plate holder(only half the translation needed) and translation of the lasers. The upper

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camera can, however, be translated individually by means of tiny screws onthe top and on the sides. To do this, one would first have to loosen the 4screws holding the plate, where the upper camera is ’hanging’ in. One cansee this set-up in Figure B.9(b) and a catalogue picture of a Pike F100B isshown in Figure B.9(a). The optics of the camera was not of interest forthis set-up and was taken off.

B.5 Linux PC

The PC that is connected to the cameras reads out the cameras. It runson CERN Scientific Linux 5 and was installed by Juha Kemppinen on13/10/2011. It has two user accounts (root and rasclic) and these are usedfor different purposes. The former is used to install new software and rightsissue handling and the latter is used for running the image analysis software.

In our case, rights issues regard the lib1394 which are FireWire rightsand if one encounters problems while starting the image analysis software,one should go (in a terminal) to the root/jSensiflexHarry-1.6.1 directoryand execute .\modprobes

When doing image analysis, one has two options. In the directoryrasclic/jSensiflexHarry-1.6.3 one can find software that shows images thecamera picks up (.\show) and software that gives a coordinate read-out com-pared to the first image it picks up (.\RasCLICTT1 ). In the ’show’ softwareone can use several commandos: s for saving one image, d for starting Rasdifanalysis and v for starting rapid images writing (10 Hz can be achieved).

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