Lau Gatignon, Catania,

 Introduction  COMPASS  NA62  SHIP L.Gatignon, SPS fixed target physics at CERN

L.Gatignon, SPS fixed target physics at CERN SHIP NA62 COMPASS

L.Gatignon, SPS fixed target physics at CERN

 All running fixed target experiments at the SPS want highest statistics with minimal pile-up. In practice the figure of merit is the time on flat top per year, i.e. the total time over which protons are extracted to the production targets of the beam lines.  The time on flat top is the product of  number of physics days scheduled  machine efficiency  duty cycle  The machine efficiency degrades if one pushes the intensity to the limits  The duty cycle for the North Area fixed target program depends on the other physics users at CERN and on the primary beam momentum (due to heating of the SPS and North Area magnets). It is the ratio of the length of the flat top(s) and the length of the super-cycle. L.Gatignon, SPS fixed target physics at CERN4

E.g:  Supercycle 14.4 (16.8) sec  Flat top 4.8 sec  Duty cycle 33.3 (28.6)% The longer super cycle (i.e s) served for machine studies in parallel with physics. In those days (before CNGS) no LHC filling! L.Gatignon, SPS fixed target physics at CERN5 Intensity in SPS Magnet current

L.Gatignon, SPS fixed target physics at CERN6 E.g:  Supercycle 46.8 sec  Flat top 9.6 sec  Duty cycle 20.5%  But high number of protons on target delivered for CNGS (~ pot over the CNGS years)

L.Gatignon, SPS fixed target physics at CERN7

 COMPASS has been running for many years with high-energy high-intensity muon beam for studies of the spin structure of the proton. Up to muons per spill at 160 GeV/c.  It has also operated with negative hadron beams for measurements of the Primakoff effect and for spectroscopy experiments. The intensity of the hadron beam was about 5 MHz.  The secondary hadron beam was of ‘modest intensity’ and required modest primary proton intensity on the T6 primary target. The (tertiary) muon beam requires the maximum incident proton flux that could reliably be delivered on the T6 target within the limits of equipment survival and radiation protection constraints. The latter are mostly related to the fact that the COMPASS experiment is located in a surface hall.  Most of the time COMPASS has been running (successfully) in parallel with the CNGS program, which has come to an end in L.Gatignon, SPS fixed target physics at CERN8

L.Gatignon, SPS fixed target physics at CERN9

COMPASS has been formally approved for running until LS2 for the following physics programme: L.Gatignon, SPS fixed target physics at CERN10  In 2014 and 2015 transversity studies with a secondary  - beam at 190 GeV/c onto a polarised target followed by an hadron absorber. This allows to increase the intensity up to 10 8 per second.  From 2016 onward high-intensity positive and negative muon beams for spin-dependent Generalised Parton Distributions. This requires again the highest proton fluxes on T6, namely ppp for a 4.8 sec flat top or ppp for a 9.6 sec flat top  These fluxes are limited by the PS and SPS radiation levels, the proton beam extraction and transport through TT20, the splitters, the T6 target and TAX beam dump-collimators, as well as radiation levels on the surface.

There are ideas, but nothing is officially proposed or approved yet. Among the ideas discussed (and presented to the European Strategy Group) we could mention  More Drell-Yan running with  - beam (as in 2014/15),  An extension of the previous muon physics program with the existing polarised target,  GPD physics with high-intensity muon beam on a polarised target (the latter needs further study),  A polarised RF-separated anti-proton beam (not yet studied),  A hyperon beam, produced in the end of the beam tunnel (not yet studied). These projects would require at some stage a consolidation of the infrastructure in the experimental hall and the last two a re-design and rebuild of the secondary beam line. L.Gatignon, SPS fixed target physics at CERN11

L.Gatignon, SPS fixed target physics at CERN12 From Andrea Bressan:

 The NA62 experiment construction is approaching completion and commissioning of the almost full detector is scheduled to start next week.  The beam line has been commissioned in a Technical Run in fall 2012 (along with part of the detector). The beam line itself was complete, but the infrastructure did not yet allow running at high intensity for extended periods.  Following the 2012 experience some minor details have been further improved, the T10 target and its instrumentation have been consolidated and the vacuum system for the decay volume is being completed and finalised. However, the final ventilation system in ECN3 and TCC8 will only be installed in  The main objective of the 2014 run is commissioning of beam line and apparatus, combined with some first physics studies, e.g. K + ➝  + at the level of the SM sensitivity. L.Gatignon, SPS fixed target physics at CERN13

L.Gatignon, SPS fixed target physics at CERN14 ~10 12 / s protons from SPS (400 GeV/c) on Be target (~1  750 MHz secondary beam: Positive Kaon fraction ~6%  p/p ~ 1%

L.Gatignon, SPS fixed target physics at CERN15 Very preliminary projection A.Ceccucci,

L.Gatignon, SPS fixed target physics at CERN16

 The NA62 requirements are similar to those of NA48 in terms of intensity. However, due to more stringent RP restrictions these conditions imply a redesign of the ventilation system and a strict air separation between the T10 target area and the experiment itself. The present layout is ok for NA62 but has no large safety margins.  In the case of a 4.8 sec flat top the combined proton requests from NA62, COMPASS and the T2 users can be satisfied: T2 + T4 (NA62) + T6 (COMPASS) = ( ) = ppp  IF one has to run with a long flat top and IF COMPASS requires maximum proton flux (?), these rates have to be increased to maintain competitive instantaneous rates: T2 + T4 (NA62) + T6 (COMPASS) = ( ) = ppp  In the latter case one must either reduce one or more of the target intensities or find ways to improve the transmission. Some ideas exist. L.Gatignon, SPS fixed target physics at CERN17

 A search for K L ➝  o  which is being studied under a PRIN grant. As the SM branching is smaller than for K + ➝  +  and as it is important to have a narrow ‘pencil beam’ to constrain the decay kinematics, such an experiment requires substantially higher proton fluxes on the K o production target than NA62. The PRIN studies used a flux of ppp on this target, assuming a long flat top.  Such requirements may need very substantial modifications to the tunnel, infrastructure (ventilation!), beam transport and beam protection and radiation protection if such an experiment were to be housed in the present NA62 location. However, in a facility similar to the one proposed by SHIP this could become more realistic.  PRIN has also looked at the possibility to look for Dark Matter candidates with a sensitivity which is limited by the presently available proton flux. L.Gatignon, SPS fixed target physics at CERN18

 An Expression of Interest was submitted to the SPSC in October 2013, proposing a search for neutral heavy leptons in a proton beam dump at the CERN SPS.  The SPSC recognises the interesting physics potential of searching for heavy neutral leptons and investigating the properties of neutrinos. Considering the large cost and complexity of the required beam infrastructure as well as the significant associated beam intensity, such a project should be designed as a general purpose beam dump facility with the broadest possible physics programme, including maximum reach in the investigation of the hidden sector  To further review the project the Committee would need an extended proposal with further developed physics goals, a more detailed technical design and a stronger collaboration.  In the mean time the collaboration has progressed along these lines, with two recent workshops, and the CERN management has mandated a taskforce to study the consequences for CERN if this project were approved. L.Gatignon, SPS fixed target physics at CERN19

 A taskforce was established by R.Saban with members G.Arduini, M.Calviani, K.Cornelis, LG, B.Goddard, A.Golutvin, R.Jacobsson, J.Osborne, S.Roesler, T.Ruf, H.Vincke, H.Vincke.  The task force report (81 pages) has been released and delivered to the CERN management. It is available on EDMS as document V1.0.  While the collaboration is working towards its Technical Proposal, some exchange of information with the Task Force members will be organised in the form of a few meetings.

 Location and civil engineering layout have been defined.  Slow extraction onto TT20 (NA channel) and replace splitter 1 by a laminated splitter/switch magnet. Then exit through Jura side wall of TDC2 into >200 m long tunnel onto the target. Flat top about 1 sec.  The target is dense (tungsten) and segmented for survival. RMS power 400 kW, 2.9 MW during the spills. This is in fact a spallation target!  The muon filter baseline is passive, but magnetised shielding is under investigation. Aim: < 10 5  per spill. This 70 m long muon filter Is followed by the detector hall (120x20 m 2 ), which is ‘underground’.  Main issues needing more work: activation at extraction ZS and target survival and manipulation.  A preliminary schedule has been prepared. Tight planning in LS2. May need some cool-down time before (ion run?).  Protons must be shared with the other fixed target users in the NA, CNGS-like.

But shortage of protons for NA62+COMPASS?

B.Goddard

The production target is installed inside an underground FE shielded bunker, accessible from the top

 Fully remote handling / manipulation of the target and shielding from the target hall - High residual dose rate (tens of Sv/hr!)  Helium environment enclosing the target and the shielding - Reduction of air activation and corrosion  Ventilation system according to ISO The idea is to have a pressure dynamic → confinement L.Gatignon, SPS fixed target physics at CERN27

 The target must be segmented to reduce temperatures and compressive stresses  Very high flow rate required (cavitation, erosion/corrosion…) - Need to check “water hammer” effect on target/cooling circuits  Full control of water chemistry (à la nTOF)  Vigorous R&D should be launched on material properties and their evolution with radiation and temperature - Ta-cladded W, Wre alloys, K-doped W alloys, etc L.Gatignon, SPS fixed target physics at CERN28

Th. Ruf

 Building a muon shield with 70 m length fulfilling the experimental requirements is feasible.  Much more work is needed to optimise the cost.  Passive shielding: -requires ~100 t of W and ~2500 t of Pb, -a large part of the W/Pb could be resold after the experiment completion, -additional material (e.g. building walls) ideally as far as possible to minimise backsplash, or filling up the space between shield and walls with iron.  Active shielding:.a combination of a magnetic field (~30 Tm) and a passive iron shoeld comes close to the experimental requirements, living with the return field is the key issue -new ideas of magnetic field configuration should be actively pursued.  In parallel, need to study (full simulation) the background caused by surviving  ’s L.Gatignon, SPS fixed target physics at CERN31

L.Gatignon, SPS fixed target physics at CERN36 ItemCost (MCHF)FTE Extraction and proton beam line Target station Muon filter (passive shield)11.0 Civil Engineering Infrastructure Total

 Beam losses will cause 1. Air activation 2. Residual dose rate increase 3. Dose to equipment (magnets, cables, etc)  “Estimated beam losses from high intensity beam (7x1013 protons per extraction) are about a factor 7 higher than for CNGS beams”, (Quotation from collimator LIU review minutes)  Already at nominal beam intensity the dose levels will be a factor 3-6 higher than in previous years. Without mitigation, this could lead to dose levels of 12 mSv/hr after a month of cool-down.  Ways to reduce beam losses have to be investigated. L.Gatignon, SPS fixed target physics at CERN37

2x

 Compared to the version discussed in the Task Force report, progress has been made. An important possible modification concerns the muon filter, which may become a magnetic shield. This allows, according to first studies, a cleaner environment for the detectors with a shorter length. This may have an impact on the civil engineering layout.  The impact on e.g. NA62 and COMPASS is similar to the one of CNGS, with probably again a longer flat top for the North Area users.  A facility of this type may be of interest for other experiments, e.g. after SHIP. It may be wise to take such aspects into account when optimising the final layout.