Beam Time 2018

(return)

Beam time 2018 started in June and it should last until end of November. June and July were devoted to commissioning of the machines after two years of shutdown with major changes to the facility: incorporation of a new control system and civil engineering works in preparation to connection of existing machines to SIS100 synchrotron, which is in construction (GaF project). However on July 13th a power converter in UNILAC RF gallery caught fire. The reason of this fire was traced to a presence of metallic pieces (eg. aluminium foil) in brand-new RF air-cooling system. The whole system had to be dismounted and cleaned, what effectively led to cancellation of experimental beam time.

The preparation notes and optics analysis for July HADES test are here.

The experimental beam time was significantly reduced and rescheduled to February-March 2019. However it was decided to perform an Engineering Run, in the end of 2018, to commission new systems and check performance of the machines after the long shutdown.

Logbook

1. November 20th, Tuesday

2. November 21st, Wednesday

3. November 22nd, Thursday

4. November 23rd, Friday (BLM - first test)

5. November 24th, Saturday (KO extraction to HADES)

6. November 25th, Sunday (HTD, HTA)

7. November 26th, Monday (quad scan GTE2QT11)

8. November 27th, Tuesday (trajectory response matrix measurement)

9. November 28th, Wednesday

10. December 1st, Saturday

11. December 2nd, Sunday

12. December 3rd, Monday (HTD)

13. December 4th, Tuesday (HTD again)

14. December 7th, Friday

15. December 8th, Saturday

16. December 9th, Sunday (HADES, final HTD)

17. December 14th, Friday

Experimental requirements for Engineering Run

HADES

1. first low energy Argon beam with long spills to pinpoint sources of beam lossed and tune the beam line.
2. ultimately fully stripped silver beam at maximum rigidity and maximum intensity.
3. spill structure tests are of great importance

HTC (source Aleksandra Kelic-Heil and Haik Simon)

1. energy 500AMeV, larger beam-spot size (sigma_x = 3mm and sigma_y = 9 mm), smaller divergence.

2. test that the beamline is working but should be accompanied by a *few* hours (half a shift to a shift) in the Cave for basic testing of our target tracking system if possible. From our side we'd be happy to work with 10^{4 ... 10}5 ions/s in the Cave at about 500MeV/u (this could be changed if necessary). The beam spot size is not critical at all, we'd expect the typical few mm but can handle up to cm for our secondary beams.

The information below was introduced before the fire accident and cancellation of Physics Run in 2018. It maybe not relevant or not up to date anymore.

Optics needed

Nominal beam performance in SIS18

Alignment

First survey results are presented here: http://sapinski.web.cern.ch/sapinski/physics/talks/GSI/2018_HEST_MM_April.pdf The alignment strategy is presented here: http://sapinski.web.cern.ch/sapinski/physics/talks/GSI/2018_HEST_MM_May08.pdf

HADES vacuum beam line inspection - September 2018

The opening of the vacuum in HADES beam line took place on September 18th in order to investigate potential nonuniformities, objects, which could cause beam losses observed in June and July.

The following locations were opened:

1. small flange on bottom of GTH2DKZ
2. large flange on the left side (looking in the beam direction) of GTH2DKY
3. large flange on the left side of GTH2DKA
4. bellow downstream to GHADKY1
5. bellow downstream GHADDK2
6. both big flanges on the right side of GHADDK3

It was found that the SEM monitor in GHADDK3 had a slightly deformed HV foil, what was repaired in situ by BI colleagues. Otherwise no objects were found inside the vacuum chambers (although the pion target part was difficult to inspect due to curvature and long path). Activation measurements (based on dust sample correction) also did not give concluding results (as expected, activation was very low and traces of beam losses have disappeared). The beam path seem to be clean and object-free. A photo below (courtesy Oksana Geithner) was taken from GHADDK2 position (right before the pion target bunker wall) toward the pion target. The whole photo is tilted. The tilted rectangle in the far perspective is vacuum chamber of GTP1MU1 dipole and the one between (which is really tilted) is GHADMU1 dipole.

Beam line was closed on September 19th.

Machine experiments

BLM calibration

Goal: Measure BLM response for a well-defined beam loss pattern and compare it to FLUKA simulations.

Beamline: HADES line, GTH2 or GTH3

Beam: Medium intensity, slow extraction (BLM in counting mode - important).

Execution: Insert a new SEM device into the beam. SEM is treated as a think target, made of 3 metal foils, 24 um each. Can be easily simulated by FLUKA. Measure response of downstream BLMs, comapre with FLUKA simulations. Important aspect measurement of the spill intensity. SEMs are not calibrated what means that spill intensity can be known within about 20%. Therefore a beam-based calibration should be tried, using a nearby particle counter assembly and saving the beam intensity in SIS18 and BLMs upstream to ensure beam shot-to-shot stability.

Interested parties: Plamen Boutachkov, Sanja Damjanovic

BLM coverage

Goal: Measure coverage of the BLM system

Beamline: HADES line

Beam: Medium intensity, slow extraction (BLM in counting mode - important).

Execution: generate various losses along the HADES eamline looking for blind spots, where beam loss does not generate signal in BLMs. Esecially look into the long empty part after TH2QD2.

optics measurements

Goal: Measure the emittance and optics functions along the beamlines

Beamline: all active, but especially the branch going to Cave A, which has screens equipped with digital cameras, allowing precise determination of beam shape and position.

Execution: Use HADES beamline as example. The simplest case is to measure beam profiles using profile grids in GTE2DK4, GTH1DK2 and GTH1DK4. There is only one magnet between GTE2DK4 and GTH1DK2 - switching dipole which is off for this optics. Therefore, using the three measurements, the beam matrix can be reconstructed and from that the twiss functions in the location of the grids, eg.: http://accelconf.web.cern.ch/AccelConf/ipac2017/papers/mopik071.pdf

(Also measure dispersion by varying SIS18 extraction energy).

Spill structure measurement

This measurement, especially for HADES experiment, is coordinated by a designated working group. It will use HADES diamond detector together with beamline BLMs and halo monitors.

Spill stability measurement

Again for HADES experiment - use data from HADES target detector and data from halo monitors to pinpoint source of beam spot on target instability.

Dynamic aperture measurement

Measure at which point the transmission drops to 50%.

http://accelconf.web.cern.ch/Accelconf/IPAC10/papers/tupeb068.pdf