Radiation


Predictions from simulation and past measurements

To be completed ...

  • Estimation from past BLM measurements: about 9 Gy/year. Presented by Plamen on 2013-03-06 here. Relevant slide here: 2013_03_06_PlaceChoice2_p10.pdf.
  • An estimate of the radiation induced by BGV is given in the ECR2: "The expected yearly dose 35 m downstream of the BGV is of the order of tens of Gy"
  • A rough calculation can also be made by comparing to teh fluence obtained in the LHCb at similar radii and longitudinal distances from the collisions, see here. One obtains about 1-2 pGy/collision at r=20cm, z=100cm. Assuming the LHC beam-gas interaction give a similar dose than a 14TeV pp collision (which is certainly an overestimate), and assuming 1e6 s/year of full intensity circulating beam with gas, one obtains about 1e6 s/yr * 2500 bunches * 11kHz * 0.01 interaction/crossing = 3e11 interactions/yr or 0.1 to 1 Gy/yr. Clearly, there is a large uncertainty, as this 0.01 assumes only interactions in the 1m region of the BGV (while gas extends over many meters). But one could easily expect a few Gy extra per year, ontop of the "background" (no-gas) radiation from the LHC.
  • SiPM fluence estimate from Quentin, see his 2014-01-29 presentation: 2300 (4900) charged particles Hz/cm2 in near (far) station, which translates into a dose of about 16 Gy/yr for 2600*1.5e11 protons at 7TeV.

Monitoring

RadMon

RadMon monitor is installed downstream of the BGV. RadMon ID: 4LM19S.

The RadMon (TO-DO: add a link) is
an active detector containing
several sensors. It provides information
about the 1MeV neutron-equivalent
fluence, the hadron fluence and the
cumulative dose.

RadMon Position

From To Position Photos
Start of LHC Run2 (June 2014) TS2 2015 (October) ~15 m downstream of the BGV
TS2 2015 (October) TS3 2015 (November) ~3 m downstream of the BGV. The top of the RadMon is 40 cm below the center of the beam pipe. DSC00318.JPG       DSC00341.JPG
TS3 2015 (November) Latest position Fixed to the L0 trigger support. About 20 cm radially from the beam axis, similarly to the detector SiPMs      

RadMon Logging/Timber Variables

Timber variable Timber description Comments
SIMA.7L4.4LM19S:FLUENCE_1MEV_N_INT Cumulated 1 MeV neutron fluence (annealing not considered) [cm-2] The sensor is a PIN diode. Initially the value is negative, because the output dropped down (normally it increases with radiation, but initially the dose is low)
SIMA.7L4.4LM19S:FLUENCE_1MEV_N_M_INT Cumulated 1 MeV neutron fluence (with annealing) [cm-2]
SIMA.7L4.4LM19S:FLUENCE_HEH_INT Cumulated hadron equivalent fluence [cm-2] Derived from the COUNTS variable on the next row. The conversion factor is: 1 Count = 1.98676e+06 HEH fluence/cm-2
SIMA.7L4.4LM19S:SEU_COUNTS_INT Cumulated SEU counts [no unit]  
SIMA.7L4.4LM19S:TID1_INT Cumulated Total Ionizing Dose without annealing [Gy]  
SIMA.7L4.4LM19S:TID2_INT Cumulated Total Ionizing Dose without annealing [Gy]  

As of September 2015 the values of these variables are compatible with zero. The proper functioning of the RadMon was confirmed by S. Danzeca. The explanation for the observed readings is that the fluence / dose accumulated so far is low compared to the monitor sensitivity. And this is due to the fact that the RadMon is new (installed in 2014) and that the radiation levels in LSS4 are relatively low. It should be possible to collect more meaningful information in the future (when we move the RadMon close to the BGV and we inject gas for the BGV operation).

Pin diodes

Old PIN Diodes in the tunnel

  • Installed 3 PIN diodes from EPFL (see chap. 7.3 in Ravotti's thesis) on some modules on 03.09.2015, all on the module insulating box surface, approximately midway between the in/out cooling lines, see pictures below (right-click on picture to enlarge):
    • PIN diode Yellow label 001 (EPFL: Si Radmon Si2_2006_016, 8.48 V, 21.11.2013) on Module 08-4L / RS side (this module is Near/Bottom/Passage and the R-S sectors are facing toward the thin exit window of the vacuum chamber)

    • PIN diode Yellow label 002 (EPFL: RADMON Si2 2006-023) on Module 02 / RS side (this module is Far/Bottom/Passage and the RS side is toward the thin exit window of the vacuum chamber)

    • PIN diode Yellow label 003 (EPFL: DOSIMETER Si- 2771 Silicon det, 2.23 V 21.11.2013) on Module 02 / TU side

    • The original EPFL labels of the three PIN diodes (yellow labels 001, 002, 003) are visible here.

These PIN diodes were removed and replaced by six fresh ones. See BGV elog entry 96.

Some temporary information on PIN diodes from Axel:

On Fri, 4 Sep 2015, Kuonen Axel wrote:
So I checked today and in fact I have a document but it is a bit updated. I will improve it on monday but few point are important with
these diodes.
1) These devices are very temperature sensitive after irradiation. So they should not be taken by hand after irradiation.
2) To avoid heating during the measure we use a pulse current of 50ms and 25 mA and we measure the voltage in the forward bias mode.
3) Federico Ravotti has done a plot showing the correspondance between the voltage and the irradiation lvl. I put it in appendix.
Reference : Development and Characterisation of Radiation Monitoring Sensors for the High Energy Physics Experiments of the CERN LHC
Acelerator, These, Frederico Ravotti, p.134
I heard somewhere that their is an updated version of this plot ( Maybe have to ask to Frederico)

For the label I don't know exactly what you used for pin diodes but the Si2 seems to be the same that Frederico uses.

New PIN Diodes in the tunnel

The Pin Diodes were installed on 14/10/2015. See BGV elog entry 96.

  • Near station :
DSC00335.JPG      DSC00336.JPG

  • Far station :
DSC00338.JPG      DSC00331.JPG

Diode ID and positions :

Module Face Diode ID
08-4L X 18
08-4L U 20
07-4L X 31
02 X 32
02 U 33
03 X 34

Manual measurements in the laboratory by Massi before irradiation (13 Oct 2015):

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf 0835_001.pdf r1 manage 1229.3 K 2015-09-03 - 18:32 UnknownUser EPFL labels of the three PIN diodes (yellow labels 001, 002, 003)
PDFpdf 2013_03_06_PlaceChoice2_p10.pdf r1 manage 259.0 K 2016-02-09 - 09:47 UnknownUser Estimation of background radiation at BGV (no gas)
JPEGjpg 2015-09-03_07.50.17.jpg r1 manage 1426.9 K 2015-09-03 - 18:25 UnknownUser PIN diode 002 on Module 2
JPEGjpg 2015-09-03_07.50.41.jpg r1 manage 1292.3 K 2015-09-03 - 18:26 UnknownUser PIN diode 003 on Module 2
JPEGjpg 2015-09-03_07.50.52.jpg r1 manage 1278.0 K 2015-09-03 - 18:26 UnknownUser PIN diode 003 on Module 2
JPEGjpg 2015-09-03_07.51.09.jpg r1 manage 1347.9 K 2015-09-03 - 18:12 UnknownUser PIN diode 001 on module BGV 08-4L
JPEGjpg 2015-09-03_07.51.22.jpg r1 manage 1285.9 K 2015-09-03 - 18:12 UnknownUser PIN diode 001 on module BGV 08-4L
JPEGjpg DSC00318.JPG r1 manage 5261.3 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00331.JPG r1 manage 6265.3 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00335.JPG r1 manage 6817.7 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00336.JPG r1 manage 6630.5 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00338.JPG r1 manage 6534.0 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00341.JPG r1 manage 5792.7 K 2015-10-14 - 15:25 UnknownUser Photos from acess on 14/10/2015
JPEGjpg DSC00348.JPG r1 manage 5493.5 K 2015-11-23 - 20:20 UnknownUser  
JPEGjpg DSC00349.JPG r1 manage 5952.5 K 2015-11-23 - 20:20 UnknownUser  
JPEGjpg IMG_7993.JPG r1 manage 2591.1 K 2015-09-17 - 15:42 UnknownUser  
JPEGjpg IMG_7998.JPG r1 manage 2402.0 K 2015-09-17 - 15:42 UnknownUser  
PDFpdf courbeirrad.pdf r1 manage 266.4 K 2015-09-09 - 09:16 UnknownUser PIN diode irradiation curve from Axel Kuonen
Texttxt manual_measurements_2015-10-13.txt r1 manage 10.2 K 2015-10-27 - 14:40 UnknownUser manual_measurements_2015-10-13.txt
PDFpdf plots_manual_measurements_2015-10-13.txt.pdf r1 manage 18.4 K 2015-10-27 - 14:39 UnknownUser plots_manual_measurements_2015-10-13.txt.pdf
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