Difference: CloudDAQ (13 vs. 14)

Revision 142006-08-17 - AndreDavid

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DAQ strategy for CLOUD prototype beamtest

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Run conditions

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Alongside the data from the sampling instruments, we need to record all the operating conditions for the run - some of which will be read automatically (e.g. temperature, pressure...) and some of which may be manually entered at the start of the run (e.g. field cage voltage). These so-called slow control values and settings will also be timestamped and recorded so that we will have an unambigous record of the run conditons associated with the corresponding data from the sampling instruments.
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Alongside the data from the sampling instruments, we need to record all the operating conditions for the run - some of which will be read automatically (e.g. temperature, pressure...) and some of which may be manually entered at the start of the run (e.g. field cage voltage). These so-called slow control values and settings will also be timestamped and recorded so that we will have an unambiguous record of the run conditions associated with the corresponding data from the sampling instruments.
 

Storage

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Miscellaneous

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  • The T11 bealine will deliver one or two pulses of charged pions, each of duration 460 ms, during the so-called the PS supercycle of 14.4 s. The beam momentum is 3.5 GeV/c, which means the pions are in the "minimum ionising" region of energy loss, typical of most cosmic rays in the troposphere. The beam size with the present magnets and CLOUD optics settings is about 1.1 m (horizontal) by 1.7 m (vertical). The time-averaged beam intensity can be adjusted between zero and 100 times the galactic cosmic ray intensity at ground level (which is about a factor 2 times the GCR intensity at the top of the troposphere). The beam intensity can be finely adjusted in this range and will be measured to about 5% precision or better with the beam telescope.
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  • The T11 beamline will deliver one or two pulses of charged pions, each of duration 460 ms, during the so-called the PS supercycle of 14.4 s. The beam momentum is 3.5 GeV/c, which means the pions are in the "minimum ionising" region of energy loss, typical of most cosmic rays in the troposphere. The beam size with the present magnets and CLOUD optics settings is about 1.1 m (horizontal) by 1.7 m (vertical). The time-averaged beam intensity can be adjusted between zero and 100 times the galactic cosmic ray intensity at ground level (which is about a factor 2 times the GCR intensity at the top of the troposphere). The beam intensity can be finely adjusted in this range and will be measured to about 5% precision or better with the beam telescope.

NTP synchronisation at T11

During a few days during August 2006 we have installed a modern P4 computer running Scientific Linux Cern 3.0.6 in the T11 counting room.

This room is connected to the CERN network via a coaxial 10 Mbit Ethernet cable. In order to assess the effect of collisions in this link on the precision with which the NTP daemon can set the system time, we have monitored the output of ntpq -p under different network loads, created using ping with different data payload sizes.

The results can be seen in the following figure:

EastHallT11NTPtest2006.png

The network delay (green dots) is the average delay from sending variable sized packets using ping for 5 seconds, every 5 seconds. There are three distinctive periods of network load: a light one, a heavy one and a final one where there is no generated network traffic at all.

The consequences on the offset of the computer's clock with respect to the time server (red diamonds) can then be seen to stabilise after 2 days. Once the heavy traffic is engaged, the clock's offset then wanders in the range of 1 to 100 ms. As soon as the network traffic is disengaged, the offset drops to the 0.1 to 3 ms range.

Our conclusion is that for the beam test of CLOUD, the coaxial link may be appropriate, but if the experiment finds NTP to be a good overall solution for their DAQ, then provisions should be made to upgrade that link.

 
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