User Guide & FAQ

Below you can find answers to some frequently asked questions.  In case you are still uncertain about something, please contact the responsible liaison physicist or the beam support during working hours. Outside working hours, please call the CCC (77500).


I have no beam! What is wrong?

First of all: Don’t panic! Many things have gone wrong, most of them simple to resolve. Follow the following troubleshooting steps:

1.      Check if the beam scintillators/wire chambers are counting particles, by clicking on the corresponding panels (consult also the CESAR Manual)

If the beam scintillators and wire chambers show noise (as above) then there is no beam in the beam line.

2.      Check the SPS Page 1, in order to be sure that beam continues to be extracted on the North Area Target.  If the spill structure and the intensities look correct, like in the figure below, then proceed to step 3.

3.     Check the “Magnet” page of CESAR. Are all the magnets “black”, or you see magnets out of reference (which you did not put on purpose) or any “red” magnets with some message as in the figure ?

In this case one of the magnets are in a “faulty” state, click on the magnet, click on “Rectifier Status”,  then click again on the magnet and “Reset”, and then “STANDBY” and “ON”. This process takes some time, so be patient. Return to the magnet page: If the magnet is not OK after this process, please call the CCC (77500) and report it, mentioning the name of the magnet, and the “info” that appears in the “Rectifier Status” panel.

4.      If none of the above applies, and you still have no beam, please call the CCC and inform the operator about the issues.   

Do I have access to the reading of the radiation alarms? I think I hear one right now, what happens ?

You can see all the radiation alarms that apply for your beam lines, by clicking in the yellow – black icon in CESAR :



In this panel, you can see the current reading of the monitors for H2 and H4. In the “Info” column, you can see the limits. In case that an alarm reading is higher than the limit, the reading will be in a different color. If an alarm exceeds the limit for more than 5 minutes, it automatically inhibits the beam. When moving collimators, please check always the radiation panel. If you hear an alarm and you are not sure where it comes from, please immediately call the CCC.

I need a threshold Cherenkov Counter or a CEDAR for PID. What is the process? What do I have to do?

The beam lines in North Area are equipped with Threshold Cherenkov (XCET) and Differential Cherenkov counters (CEDAR). The threshold Cherenkov counters allow by adjusting the pressure to tag different particles, depending on the refractive index of the radiator gas. With combinations of two threshold Cherenkov counters, most particle species can be tagged efficiently, especially in high momenta. Please investigate the radiator gas you need (N2, CO2, He, or R134) according to your PID schema and in collaboration with the responsible physicist, inform the corresponding technical service well in advance, since gases are not always available.

What is the timing signal that I receive from the SPS ?

There are three available signals:

  • WWE (warning-warning-extraction) : typically ~1s before particles arrive,

  • WE (warning extraction) : typically few 10 ms before particles arrive,

  • EE (extraciton-end) : at the end of the extraction.

The signals are 2 us TTL signals, adjusted each time to the SPS super-cycle timing. For more questions on that, please contact the responsible physicist.

Can I check from home the status of my test-beam ? Can I see the monitors that I see through CESAR from home?

Unfortunately due to restrictions of the CERN technical network, you cannot access CESAR from home. However, we have established for you a system that reads the monitors of the line, and you can check the beam status. The system is available here. For information, please contact the beam support.


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