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HiRadMat Project - 841182
HiRadMat Project
Date: 09/02/16
Functional Specification
Helium gas flow and purity in CNGS
Abstract
This Functional Specification defines the requirements for the helium gas flow and
helium purity control in the two helium tanks located in the TCC4 target chamber of the
CNGS facility.
Prepared by :
Konrad ELSENER
Valeri FALALEEV
Stephane RANGOD
Checked by :
[Checkers]
(1)
Approved by :
[Approvers]
Approval group members:
Members of the CNGS Project Team and the CNGS Technical Working Group
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HISTORY OF CHANGES
REV. NO.
DATE
PAGES
DESCRIPTION OF CHANGES
2.0
2003-10-11
1-9
final version, including changes after approval process
1.0
2003-09-23
1-9
version for approval
0.2 draft
2003-08-29
1 - 10
includes comments by V. Falaleev and S. Rangod
0.1 draft
2003-08-20
1 - 10
Circulated as very early draft version
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TABLE OF CONTENTS
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1.
1.1
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1.1.1 [level 3 title] ................................................Error! Bookmark not defined.
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1. SCOPE
This Functional Specification summarizes the requirements on the helium gas flow and
purity control in the helium tanks located in the target chamber TCC4 of the CNGS
facility [1-5]. The CNGS Web pages should be consulted for the latest information on
the CNGS layout and installations (http://cern.ch/cngs).
2. HELIUM GAS TANKS AND CNGS OPERATION
2.1 BRIEF DESCRIPTION OF THE CNGS NEUTRINO BEAM
A schematic view of the main components of the CNGS facility is shown in Figure 1.
Figure 1: Main components of the CNGS facility.
The SPS proton beam is extracted at 400 GeV in LSS4 and guided over about 840 m
through TT40/TT41 to the CNGS target station T40.
The SPS protons colliding with the target produce secondary particles. The positively
charged component of the secondary hadron beam is focused by magnetic lenses
(horn and reflector) while the negatively charged particles are de-focussed into the
shielding along the beam. The positive pions and kaons decay in flight into muonneutrinos and muons in a 1 km-long evacuated decay tube. Protons not interacting in
the target, as well as hadrons which have not decayed, are absorbed in the hadron
stopper.
The muon beam from the decays is degraded in the hadron stopper but a high flux of
muons still reaches the first muon detector chamber. Only the higher energy muons
will reach the second muon detector chamber, separated from the first one by 67 m of
rock. The neutrinos are travelling in the direction of Gran Sasso.
2.2 PARTICLE LOSSES - HELIUM OR VACUUM TANKS
The intensity of the neutrino beam at Gran Sasso is given by the production rate of
positively charged pions and kaons, and by the fraction of these secondary particles
which are decaying while flying in the direction of Gran Sasso.
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Therefore, the performance of the CNGS facility in the region after the target is
determined by two main factors:
(1) The quality of the pion/kaon beam produced by the magnetic lenses (horn
and reflector). This implies optimising the focusing of the pions/kaons
produced into a parallel beam in direction of Gran Sasso.
(2) The amount of material along the trajectories of the kaons and pions: reduce
the losses of pions and kaons before they decay by limiting the nuclear
interactions in material.
In analogy to the solutions chosen at the WANF neutrino beam facility [8], material in
the target chamber is reduced by inserting helium tanks between horn and reflector,
as well as in the region downstream of the reflector. The main advantage of a helium
over a vacuum tank is the reduced amount of material needed to build a tank
operating at atmospheric pressure.
Figure 2: Layout of the CNGS facility
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2.3 THE TARGET CHAMBER TCC4
Figure 2 gives a schematic view of the CNGS facility. The target chamber, called TCC4,
is located at the end of the proton beam tunnel. It is about 120 metres long and
houses the target station, the horn and reflector (focusing devices) and two helium
tanks. The layout drawing of the target chamber, showing all the equipment, but also
the shielding foreseen to be installed along the beam line, can be found at
https://edms.cern.ch/document/310296 [see reference 6].
2.4 THE HELIUM SYSTEM
The two helium tanks are located in TCC4 and are connected in series by two pipes
(“IN” and “RETURN”) to the existing building 930. No active equipment will be located
in TCC4 or the service gallery TSG4 - building 930 will house a gas system and the
controls equipment necessary to operate the system. A layout of building 930 showing
the space reserved for the helium system is appended on page 9.
2.4.1 THE HELIUM TANKS IN TCC4
The exact start/end co-ordinates of the two helium tanks in TCC4 are evolving
together with the detailed design of the equipment in this region of CNGS.
Approximate dimensions of the helium tanks can however be given.
The first helium tank, located between horn and reflector, is approximately 30 metres
long. The first 6 metres are embedded in an iron collimator - in this part, the first
helium tank has a diameter of 0.80 metres, for the rest of its length the diameter is
1.20 metres.
The second helium tank is approximately 47 metres long and has a diameter of 1.20
metres.
The two helium tanks are connected in series, with - in both tanks - the IN pipe
connected near the highest and the OUT pipe connected near the lowest point of the
tank.
2.4.2 THE HELIUM GAS SYSTEM IN BUILDING 930
The system will be connected via all-metal pipes from building 930 to TCC4, and back.
The return helium will be lead through the instruments described below, then left into
air.
The helium gas system should consist of








two racks of helium gas bottles, with an automatic (pneumatic) system to
switch from one to the other
a flow meter allowing a very large flow (for filling the tanks): 800 litres/hour
a flow meter for standard operation with 10 mbar overpressure and a small
flow: 140 litres/hour
an oxygen metre on the “return” gas line to control the helium gas purity
a small pump for the calibration of the oxygen metre with air
2 safety pressure bubblers, one in the “out” and the other in the “return” gas
line, safety limit adjusted at 20 mbar
an overpressure safety valve between bottles and bubblers
OPTIONAL: an “on/off” flowmetre, indicating gas flow on the “return” gas line
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3. EXISTING EQUIPMENT FROM WANF
The gas system as described in 2.4.2. exists and can be recuperated from WANF [7],
with the exception of the optional “on/off” flow metre, which would need to be
added.
4. REQUIREMENTS FOR THE HELIUM FLOW
4.1 GAS SUPPLY AND CONTROLS
The supply of the “batteries” of helium gas bottles, connection to the gas system,
regular control and exchange of bottles in time will be the responsibility of the GDS
team in EST/LEA (see [8]). The existing automatic “bottle changer” has an output
which allows to read which rack of bottles (A or B) is being used. This information
must be read out and made available to the CNGS beam control system.
Gas supply must be continuous, i.e. the helium gas flow must be available also in
shutdown periods.
4.2 GAS FLOW CONTROL
Information on the gas flow can be obtained - although indirectly - from the oxgen
meter (see 5.1).
OPTIONAL: The helium gas flow is to be controlled on the return line by a simple
“yes/no” electronic flow metre. “Yes” corresponds to a gas flow of larger than 0.5 litres
per minute, with an allowed error of 20%.
4.3 DATA ACQUISITION, DATA HANDLING, ALARMS
See 5.3. below, for control of gas flow by using the oxygen meter.
OPTIONAL: The status of the gas flow meter (“yes” or “no”) is to be checked every
hour, and the status written into a log-file whenever there is a change of the status. If
there is no change, the status is logged at 12:00 noon every day. A “low level” alarm
must be created for the operators in the SPS control room, indicating that the helium
gas flow has stopped and that action by a specialist is required.
5. REQUIREMENTS FOR THE HELIUM PURITY
5.1 OXYGEN METRE
It is suggested that the existing oxygen metre from WANF is being re-used.
5.2 CALIBRATION OF OXYGEN METRE
A calibration of the oxygen metre with air must be performed once per year.
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5.3 DATA ACQUISITION, DATA HANDLING, ALARMS
The oxygen metre provides a voltage indicating the proportion of oxygen in the return
helium gas line. This voltage is to be checked every hour, and helium purity written
into a log-file whenever there is a change of more than 1%. If there is no change, the
status is logged at 12:00 noon every day and written into a log-file. The reading is to
be compared with a pre-defined, but changeable limit value (for example a level which
corresponds to 95% helium purity), and a “low level” alarm must be created for the
operators in the SPS control room if the oxygen level is above this pre-defined limit.
The alarm must indicate that helium purity is bad and that action by a specialist is
required.
The information read from the oxygen metre must be made available to the CNGS
beam control system.
6. SAFETY AND REGULATORY REQUIREMENTS
The equipment used must meet the safety guidelines put forward by the CERN
Technical Inspection and Safety Commission (TIS). TIS have issued safety documents
in compliance with LHC-PM-QA-100 rev1.1, and the guidelines in these documents will
be incorporated.
7. REFERENCES
[1] K. Elsener Ed., The Cern Neutrino Beam to Gran Sasso (Conceptual Technical
Design), CERN 98-02, INFN/AE-98/05, 1998.
http://doc.cern.ch/cgi-bin/setlink?base=cernrep&categ=Yellow_Report&id=98-02
[2] R. Bailey et al., The CERN Neutrino Beam to Gran Sasso (NGS), CERN-SL-99-034DI, 1999,
http://doc.cern.ch/archive/electronic/cern/preprints/sl/sl-99-034.pdf
[3] A.E. Ball et al., CNGS: Update on Secondary Beam Layout, SL-Note-2000-063
EA, 2000,
http://doc.cern.ch//archive/electronic/cern/others/sl/sl-note-2000-063.pdf
[4] A.E. Ball et al., CNGS: Effects of Possible Alignment Errors, CERN-EP/2001-037,
CERN-SL-2001-016 EA, 2001,
http://doc.cern.ch/archive/electronic/cern/preprints/sl/sl-2001-016.pdf
[5] M. Clement et al., Update of changes to CNGS layout and parameters,
http://proj-cngs.web.cern.ch/proj-cngs/PDF%20files/CNGSupdate_note_final.pdf
[6]
Layout
drawing
of
https://edms.cern.ch/document/310296
the
target
chamber
area,
[7] G. Acquistapace et al., “The West Area Neutrino Facility for CHORUS and NOMAD
experiments (94-97 operations)”,
http://doc.cern.ch/archive/electronic/cern/preprints/ecp/ecp-95-014.pdf
[8] Meeting on CNGS helium gas system, 10 December 2002, summary notes see
https://edms.cern.ch/file/366422/1/CNGS_helium_meeting_121202.pdf
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