Beam Documentation for NA48/NA62

GEOMETRY - BEATCH

The updated geometry files 'Beatch' for the P42 and K12 beams to experiments NA42 and NA62 are listed here with descriptions of their contents: - (click here for a short description of the file format)

• P42-1997 for the proton transport from the upstream target station T4 (shared with beams H8 and H6 to EHN1) to the KL production target, T10. This has remained unchanged up till and including 2002.
• P42-2003 is similar to P42-1997, but shows the last (redundant) horizontal steering magnet (MDXH045835) replaced by an additional vertical bending magnet (BEND 12): MCWV045834. This is required in 2003 to attain zero angle of incidence of the proton beam onto T10.
• P42-2011 updated 23/03/17 to show the separation of BEND 7 (MBNH043520-MBNH043565) into BEND 71 + BEND 72, otherwise has the same sequence of beam elements as P42-2003, which served to transport primary protons onto the T10 target at zero angle for experiment NA48/2. In preparation for experiment NA62, the T10 target station and the axis of the cold vacuum tube traversing the LKr calorimeter have been resurveyed. In order for the new K12 beam, produced at zero angle, to pass through these two fixed points, displacements of the reference axis by dx = +6.0mm, dx'= +0.0042mr (horizontally) and by dy = -3.5mm, dy'= +0.0206mr (vertically) are required at T10 - starting from the entrance of the magnet MBNH043718 in the P42 beam as a point of origin. These displacements are achieved by changing the angles of deflection of Bends: B 8 + B 9 (horizontally) and B10 + B12 (vertically) and realigning all elements downstream of MBNH043718 accordingly.
• P42-2021 updated 29/07/21 is similar to p42-2011, with an additional QNL installed at position QNL 043710, adjacent to - and reinforcing - Q18 (QNL 043714), with which it is connected in series. This enables the horizontal,vertical beam magnifications from T4 to T10 to be reduced to +0.44,-0.66, respectively, if needed, (as in 2018), instead of the standard +0.5,-1.0, without overloading Q18.
• P42-2023B, dated 28/03/23, takes into account the realignment of the beam during the 2022-23 shut-down, following the removal of BEND 6 (10 MCAH062119-149 - a relic from the P61/P62 beam link) and the installation of additional SEM beam monitors.
• K12-1997 for the beam line from the KL target to NA48, as it was believed to have been in 1997 and has probably been used in the reconstruction programs!
• K12mod97 for the beam line based on the new longitudinal calibration of detector positions downstream of the KS target (M.Chambardon).
  Compared to K12-1997:
  • The KS collimator and AKS are both displaced downstream by 2mm;
  • WC1 is displaced downstream by 2mm;
  • WC2 is displaced upstream by -3mm, i.e. the distance WC1-WC2 is shortened by 5mm;
  • MNP33 is displaced upstream by -2mm;
  • WC3 is displaced upstream by -3mm, i.e. the distance WC2-WC3 is unchanged;
  • WC4 is displaced upstream by -5mm, i.e. the distance WC3-WC4 is shortened by -2mm;
  • The LKr calorimeter and following detectors are displaced upstream by -15mm.
• K12-1998 for the beam line in 1998 is similar to K12mod97 with the addition of the positions of eta targets 1 and 2 and Mu-Veto1 and its surrounding Iron walls closed up against Mu-Veto2.
• K12-1999 (dated 10/19/98) is like K12-1998 as far as the experiment is concerned and has the same beam vacuum tube, made of C-fibre composite, introduced in 1998. The only change is the addition of a new vertical steering magnet (TRIM 4): MDXV101059 for the proton beam upstream of the KS-target.
• K12-2000 (dated 01/26/00) describes the situation for e'/e in 2000, with the Kevlar window, beam tube and WCs removed and replaced by 'dummy chambers', i.e. the He-tank forms a continuation of the blue vacuum tank. In addition, a new ionization chamber: XION101255 is installed as a monitor just upstream of the (Mainz) Beam Counter at the downstream end of the beam line.
• K12-KS00 (dated 01/26/00) describes the situation for running the intense KS beam in 2000. It shows the AKS crystal goniometer (XAKS101126) and counter assembly removed and the KS beam entirely contained in vacuum through a Ø = 215mm vacuum connection at the exit of the collimator. The KL aperture of the final collimator(TCX101125) is filled with 3 x 0.5m long bronze 'plugs'. The last vertically deflecting magnet upstream of the KS-target (MCWV101117) is replaced by a stronger magnet: MBNV101116, which would allow 400 GeV/c protons to be targetted at a smaller angle.
• K12-2001 (dated 13/11/01) gives a description of the beam as it was in 2001: The previous magnet (MCWV101117) upstream of the KS-target is restored, the KL aperture plugs removed, the AKS assembly remounted, the reserve Kevlar window and repaired WCs 1, 2, 3 and 4 are installed in their REVISED surveyed positions together with the new beam tube (made of Al). The (revised) differences in longitudinal spacings with respect to 1999: dz(2001-1999) are indicated where appropriate.
• K12-KS02 (dated 6/05/02) describes the layout of the High-Intensity KS beam for NA48/1 in 2002. Compared to K12-KS00, it shows the KS-target unit (XTGU101120) displaced upstream by 0.234m to allow the introduction of an element (XTGU101121) carrying a choice of x-, y-motorized photon absorbers, centered 0.600m downstream of the target. These consist of Platinum rods, 2.6mm in diameter and 24, 32, 40mm in length - in addition to an empty position. The last 1.5m length of the KL beam aperture through the sweeping magnet MTNV101122 is filled with bronze plugs. The KS beam aperture through this magnet is followed by a stainless steel collimator (COLKS) containing the KS beam-defining, tungsten inserts. It is surrounded by an additional, 0.4m (~0.5T.m) dipole magnet MDXV101125 and by the final 0.6m steel shielding (TCX101126). The total length of the KS beam from target centre to collimator exit is 6.236m. The Kevlar window, WC2-4 and the new Al beam tube are shown in their (revised) K12-2001 positions. After repair, WC1 is shown in its resurveyed position, 1mm downstream of its 2001 position.
• K12K+K-03 (dated 9/05/03) gives a description of the new K12, simultaneous K+/K- beam derived from target station T10, for NA48/2 in 2003. KABES(1+-) and KABES(2) are shown, each occupying a length of 202mm inbetween 50 micron Mylar vacuum exit and entrance windows, which are mounted on a common, pre-aligned support. The final collimator (TCX101102) ends at 102.0m from the target (24.0m upstream of its previous position) and 2x12m sections of blue tube are added to extend the fiducial region for decays. The longitudinal positions of both (retractable) eta-targets (now 38.622m apart) are shown. The Kevlar window and WC1-3 have been realigned, so as (together with WC4) to be centred on the common K+/K- (previous KL) beam axis. Their actual, surveyed, horizontal (x) and vertical (y) positions are noted, (WC1 according to the survey of 6th.May 2003, following its repair and reinstallation). The longitudinal (z) position of WC2 is measured to be displaced upstream by 1mm compared to 2002. The last Anti-counter pocket (AKL7), WC4, He-tank end-cap, beam vacuum tube and HODO 1 + 2 remain in their past configuration, following the decision not to include the KTeV-TRD. The Mainz beam monitor has been moved upstream to leave space at the downstream end of the beam for the new Pisa Beam Monitors, shown as: BEM (1+2), (motorized in y and separately in x, allowing either to be centred on the straight- or one on each of the + and - deflected-beams).
• K12K+K-04 (dated 25/06/04) describes the layout of the K12 simultaneous K+/K- beam for 2004. Compared to the beam used in 2003, the horizontal beam steering magnets:TRIM 1A and TRIM 1B, which were connected in series, have been connected to independent power supplies and appear as TRIM 5 and TRIM 1, respectively. Also, the surveyed (x,y,z) positions of the replacement Kevlar window and of WC1 are given, whereby WC1 appears displaced downstream by 2 mm compared to its 2003 position. The aperture diameters of the effective momentum-selecting, defining, cleaning and final collimators for the narrow-band K+/K- beam are indicated.
• K12K+K-07 (dated 26/03/07) describes the layout of the K12 narrow-band K+ or K- beam for the NA62 Ke2/Kmu2 measurement, 2007. Compared to the beam used in 2004, the hardware changes are that the first 2 of the 4 toridally-magnetized muon collimators (SCRAPER 1A+2A) and the two KABES(1+-)+(2) are removed and replaced by continuous vacuum. A U-shaped steel girder is mounted on the supports of the charged hodoscope to carry a 2520mm wide, 180mm high and 50mm thick electron absorber, built up of 5mm thick Pb plates (PB ABS.). This is aligned so as to cover 3 strips of scintillator of HODO 2(H) just below the central beam tube.
• Otherwise, all the magnet currents are increased to select either +(down) or -(up) 75 GeV/c beams through momentum slits in the front-end achromat 'TAX(17),(18)', which are narrowed to decrease the momentum bite to (1.8 - 2.2)% (rms). The smaller-aperture (x 1/2) defining collimator (XCLD-BB) is used to decrease the beam acceptance (to +-0.18mr) and hence the transverse size in each plane (and also to allow the smaller dp/p to be defined). The quadrupoles are set to provide a beam of approximately constant size through the decay region and the detectors. The last horizontal steering magnet (TRIM 3) is set to deflect the +(-) beams by +(-)0.30mr (later decreased to +(-)0.22mr) on entering the decay region. This allows the spectrometer magnet (MNP33) to be run at +(-)1200/2400 A. current (as for NA48), giving -(+)3.5mr deflections to the beams, whilst allowing them to pass through the apertures of the downstream detectors.
• K12K+K-08 (dated 3/10/08) describes the narrow-band K+ or K- beam as used for the completion of the NA62 Ke2/Kmu2 measurement in 2008. The beam vacuum tube at the exit of the final collimator (TCX 101102) is replaced by the old (NA48 - KL + KS beam) tube of internal diameter 95mm, to allow the installation around it of a 1400 x 1400mm^2 HODOSCOPE to record particles originating upstream of the fiducial decay region.
• K12K+K-09 (dated 24/08/09) describes the changes to the layout for 2009 to accommodate tests of the 'Module 0' Large Angle lead-glass Photon Veto detector (ANTI 0), as well as of the first 'Straw prototype', mounted vertically in the 3m section No. 5 of the blue vacuum tank. The 6m-long section No. 1 of the vacuum tank is removed and sections Nos. 6, 7 and 2 displaced upstream by 1.61m to allow the 1.55m-long module to be introduced between section Nos. 2 and 3. The module is mounted with its final orientation, but with its 0.06m thick connecting 'Flange' at its upstream end. Thus the man-hole is situated on the Saleve side of the tank. A new vacuum tube (of 95mm inside diameter over the first 0.145m, followed by 320mm diameter over the next 4.430m length) is needed to join the exit face of TCX 101102 to the existing, 320mm diameter sections of tube (which include the IN/OUT ETA-TARGET and the vacuum-separation valve (VXSV) upstream of the blue tank).
• K12HIKA+ (dated 28/05/19) represents the beam and detector layout for experiment NA62 to measure the ultra-rare decay: K+ -> pi+ nu nubar. The beam is described in Chapter 2 of the NA62 Technical Design Report, NA62-10-07. The principal beam-line and detector components are listed here as installed and used for data-taking in 2016, 2017 and the beginning of 2018.
• The 75 GeV/c, narrow momentum-band (+-1.0 % rms), secondary beam is derived from the existing target station T10. The elements are installed along the resurveyed K12 beam line pointing from T10 towards the exit of the LKR calorimeter, (see the description of the P42 beam: P42-2011, above). The beam employs a triplet of radiation-resistant, acceptance quadrupoles to focus the beam to the mid-point of a 'front-end achromat', which is composed of four (MTRV) dipole magnets to provide momentum selection and recombination. In the centre of the achromat the wanted beam is displaced vertically downwards by 110mm, allowing its momentum band to be defined and primary protons and unwanted secondary hadrons to be dumped in two motorized dump/collimator units (XTAX). In between these, a tungsten radiator (XCON) of variable thickness (0 - 1.3 X0) is located, in order to suppress the e+ component in the beam.
• Following the achromat dipoles, a triplet of quadrupoles refocuses the beam through a redefining collimation and muon-sweeping stage. A subsequent quadrupole doublet then renders the beam parallel, matching it to a W-type CEDAR differential Cerenkov counter, which is filled with N2 gas at a pressure of 1.73 bar to tag K+ at 75 GeV/c momentum. The CEDAR is equipped with 8 arrays of SiPMTs (KTAG), which detect the Cherenkov light passing through a radial diaphragm onto a system of mirrors to identify the K+.
• A final quadrupole doublet is used to match the beam to the spectrometer and tracking system, whilst limiting the beam size through the apertures of the downstream detectors. The beam tracking system consists of three 'GigaTracKer' stations, composed of Si-pixel arrays each of active size: [+-30mm (horizontally) x +-13.5mm (vertically)], installed in vacuum. These are arranged so that the space between GTK 1 and GTK 3 is occupied by a 'second achromat' composed of four, vertically deflecting, C-shaped dipole magnets (MCBV), with the yoke ofthe fourth magnet oriented UPwards. During 2017 the last 1.0m of the gap of this magnet was filled with Cu inserts, covering the region: [+70mm < y < +250mm] above the beam vacuum chamber to intercept certain pi+ from upstream K+ decays, which could otherwise enter and cross the fiducial region. Use is made of the return fields in the yokes of the third and fourth magnets to enhance the 'defocusing' action for mu+ produced by a 5m-long, toroidally-magnetized iron 'SCRAPER', which is located in the momentum-dispersed section between the second and third magnets. Here its lower jaw serves to deflect away mu+ (of momenta <~50 GeV/c), which become separated from the beam. In addition, the upper jaw of the SCRAPER blocks the undeviated and upper paths through the achromat, thereby ensuring that no punch-through neutral (neutrons, K0L) or negatively-charged hadrons (pi-, K-), can be transmitted to the end of the beam. GTK 2 is located just after the SCRAPER, where the +75 GeV/c beam axis has a parallel, downward displacement of -60mm and hence a dispersion of 0.6mm/% dp/p to provide the momentum measurement. GTK 3 is placed after the final cleaning collimator and is followed by a series of 'guard-ring' scintillation counters (CHANTI 1 - 6), of inner / outer dimensions: [95mm x 65mm] / [300mm x 300mm]. The final collimator (XCHV101101) consists of 4 motorized steel blocks, 1.0m in length and [120mm x 120mm] in cross-section. These were adjusted to provide a rectangular opening of [+-35mm x +-20mm] in 2016,[+-33mm x +16 -17mm] in 2017 and [+-33mm x +-18mm] upto 18.June 2018, so as to absorb background particles SUROUNDING the beam, whilst the CHANTI rate remained on a minimum plateau.
• GTK 3 is immediately preceded by a horizontally-deflecting steering dipole magnet (MDXH), used to direct the beam away from the axis by +1.2 mr towards the Jura side. This angle is chosen so that the subsequent spectrometer magnet (MNP33) deflects the beam back through the central aperture of the LKR calorimeter.
• The sections of the decay vacuum tank ('blue tube') are linked to the former 'He tank' and the whole volume evacuated to ~10-6 mbar pressure. The 'He tank' is extended to house the spectrometer, which is designed to detect and track charged particles from K+ decays in the (60m long) fiducial region following GTK 3 and also to provide hermetic coverage against pi- (from Ke4 decays) of momenta < 60 GeV/c. Tracking is performed by 4 STRAW chambers, comprising 4 views (u, v, x, y-projections), each composed of 4 planes of 2100mm-long, 9.8mm-diameter, straw tubes, leaving ~118mm wide/high gaps around the (displaced) beam trajectory, (corresponding to 7 straws missing in each plane of each view). The u, v, x, y-coodinates of the centres of the straws nearest the beam are indicated in the file. STRAW chambers 1 - 2 and 3 - 4 are located, with appropriate lever-arms, upstream and downstream of the large- aperture spectrometer magnet, MNP33. The magnet provides a pT-kick of -270 MeV/c giving a -3.6mr deflection to the +75 GeV/c beam. In conjunction with the upstream deflection of +1.2mr, the beam thereby converges to cross the undeviated axis at a point 2.8m downstream from the mid-plane of the LKR calorimeter. The LKR CAL is followed by the Muon Veto, comprising a new, half-HAC (MUV 1) preceding the old front-half HAC, turned front-to-back (MUV 2), a 0.8m-thick iron wall and a new, fast hodoscope (MUV 3), all installed on longitudinal rails. The hodoscope is composed of scintillator pads, viewed directly by PMTs from the rear, and covers an area of [2640mm x 2640mm] with a central hole of 206mm diameter around the beam tube. Downstream of MUV 3, the beam is deflected to the Saleve side by a 2m-long magnet (MBPL-TP) with 200mm gap, which provides a pT-kick of -990 MeV/c (-13.2 mr deflection).
• The space between the end of the spectrometer and the LKR CAL is occupied by a RICH counter, housed in a cylindrical, steel vessel, made up of four 'Drums', capable of being evacuated. It occupies a total length of 17.7m between the central flanges of the RICH-entry window (of 2200mm outer diameter, off-set by x=+34mm to follow the beam) and the Al exit end-cap (of o.d. 2800mm, centered at x= +2mm). Mirrors of 34.000m radius of curvature are positioned at the focal length of 17.000m from two arrays of PMTs, located on each side of the upstream section. The counter is filled with Ne gas at slight over-pressure. It is traversed by an Al beam vacuum tube, made in sections of inner diameter 168mm and alternating 1.05(+-0.15)mm and 5mm wall-thickness over fractions of 0.94 and 0.06 of its length, respectively, making it equivalent to a tube of ~1.3mm uniform thickness.
• The decay vacuum-tank and spectrometer are interspersed by 11 annular, large-angle photon-veto counters, LAV 1-11, which surround the acceptance cone for charged-particles. LAV 1- 8 are each composed of 5 (LAV 9-11 of 4) staggered and overlapping rings of 370mm-long lead-glass blocks attached to PMTs. The blocks and their PMTs are oriented radially and are mounted inside 1.55m (1.43m)-long sections of vacuum tank, which each incorporate a man-hole/pumping port and cable feed-through flange.
• Downstream of the RICH, a 12th. module (LAV12) stands, in air, mounted on longitudinal rails, occupying a length of 0.70m and carrying 4 layers of lead-glass blocks, which extend outwards from the active area of the LKR CAL. The front of the LAV12 module serves to support a new charged-particle hodoscope (NewCHOD) made of scintillator pads defining a sensitive area between inner and outer diameters of 280mm and 2140mm, each viewed by 2 SiPMTs. LAV12 is followed by the 2 planes (CHOD(x)+(y)) of the NA48 charged hodoscope, mounted on the same rails. An additional hodoscope (MUV 0) is mounted on the Jura side of the RICH Al end-cap (covering a square region: [+1545mm < x < +2945mm], [-700mm < y < +700mm]), to intercept a cluster of muons that would otherwise escape detection. In front of the LKR CAL, an Intermediate Ring ('Shashlyk'-type) Calorimeter, IRC, made of two modules of inner aperture diameters 120mm and 122mm, respectively, surrounds the beam at an off-set of x=+10mm. It has an outer diameter of 290mm, centred on the LKR cold entry flange (of o.d. 286mm) at an off-set of x = -2mm. The IRC is thus designed to cover the central, inactive region of the LKR, so as to intercept all photons from the fiducial region, that may have traversed the walls of the tube passing through the RICH. The IRC modules are traversed by stainless-steel vacuum tubes of inner diameters 118mm and 120mm, respectively, and 0.8mm wall-thickness. The IRC, LKR and 12 LAV counters, as well as a final Small-Angle ('Shashlyk') Calorimeter (SAC), covering an area of [205mm x 205mm], centred on the axis at a (revised) distance of 11.756m downstream from the centre of the MBPL-TP magnet, - together assure hermetic coverage for vetoing photons emitted at all angles out to ~45mr from K+ decaying in the fiducial region. Adjacent to the Saleve side of the (i.d. 318mm) vacuum tube following the MBPL-TP magnet, a hadron sampling calorimeter (HASC), consisting of a stack of 3 horizontal x 3 vertical modules, each of [100mm x 100mm] cross-section, serves to detect high-energy (~40 GeV/c) pi+ escaping along the beam tube from K+ -> pi+pi+pi- decays and e+ from conversion of gammas from K+ -> pi+pi0 decays.
• The SAC and the +75 GeV/c beam, which is deflected to the Saleve side, are contained inside a vacuum tube of i.d. 598mm, which extends 9.0m into a 'tunnel' of [3.0m x 2.5m] cross-section, extending ~10m into the ground downstream of the ECN3 cavern. The beam is finally absorbed at the end of this tunnel in a dump, composed of an iron core surrounded by concrete blocks (of [2.4m x 2.4m] lateral extent and 2.8m length). To monitor the beam profile and intensity, an analogue wire chamber (XWCM) and an ionization chamber (XION) are placed on the deviated beam line between the vacuum exit window (i.d. 160mm) and the dump.
K12HIKA+T (dated 28/05/19) describes the beam as used for data-taking after TS1 (18.-21.June), 2018. The previous, adjustable, 4-jaw final collimator(XCHV101101) was replaced by a fixed steel collimator (TCX 101101), 1.2m in length, of outer dimensions (1700mm x 1800mm) and central, race-track shaped (76mm x 40mm) aperture, designed to absorb all pi+ from upstream K+ decays, which could pass outside the aperture.
K12HIKA+D (dated 17/05/2021) describes the beam layout as modified during LS2 for renewed data-taking in 2021.
• The changes are:
• The four magnets of the Second Achromat (MCBV101082, 085, 095, 098) are all displaced upstream by dz = -0.32m. In addition, the two central magnets (MCBV 085, 095) are lowered by dy = -5mm to y = -55mm and the fourth magnet (MCBV 098) by dy = -20mm. The strengths of all four magnets are increased by 5 %, so that the parallel, downward displacement of the beam is increased from -60mm to -63mm and hence the momentum dispersion becomes 0.63mm/% dp/p. GTK 2, located in this section, is displaced upstream of the SCRAPER (XCMV101090), which is itself lowered by dy = -5mm to y = -55mm, so the lower face of its vacuum chamber is at -19.5mm and its lower (magnetized) jaw at -22mm from the beam axis. MCBV 082, 085, 095 are now connected in series (= BEND 1A, -1B, -1C), leaving MCBV 098 (= BEND 2) with an independent power supply, to allow it to be changed to the same polarity as BEND 1C for data-taking in Beam Dump mode.
• A 4th. GigaTracKer station (= GTK 0) is housed in a common, 320mm-long, vacuum vessel, 50mm in front of GTK 1,(which is itself displaced downstream by dz = +25mm).
• The Fast Sector Valve (of 100mm diameter free aperture), in front of the final collimator (TCX 101101, installed in 2018), is displaced upstream by dz = -3.93m (to become VXSV101096). It is introduced on the y' ~ +3 deg. upward slope between the third and fourth magnets of the achromat (MCBV 095, 098). TCX 101 is displaced upstream by dz = -0.099m.
• Longitudinal spaces, dz = 0.19m and dz = 0.10m, thereby made available between MCBV 098 and TCX 101 and between TCX 101 and MDXH 102, serve to locate 2 planes of VETO-COUNTERS (VETO 1 + 2), interspersed by a lead photon converter, and a third plane (VETO 3). These cover the regions [-60mm < x < +60mm], [+22mm < y < +102mm] and [-22mm > y > -302mm], respectively, and are introduced above and below thin-walled vacuum chambers of race-track cross-section (78mm x 42mm), centred on the beam. The Cu inserts introduced into the fourth magnet (MCBV 098) in 2017 are removed, so as not to block the path of background particles towards the new VETO-COUNTERS.
• A new anti-counter, ANTI 0, covering a surface of inner/outer dimensions:: [236mm x 236mm]/[2160mm x2160mm] is added at the beginning of the decay fiducial region. It is composed of 284 [124mm x 124mm] scintillator tiles, surrounding a 300mm-long section of beam tube of inner diameter 192mm (previously 312mm), placed UPSTREAM of the Gate Valve (VAC. O=318) at the entrance to the vacuum tank ('blue tube').
• The modules of the sampling calorimeter (HASC) on the Saleve side of the 318mm diameter vacuum vessel following the downstream beam-deflecting magnet (MBPL-T) are rearranged in 3 layers to cover the range [-180 mm < x < -480 mm, -150 mm < y < +150 mm]. A second sampling calorimeter (NewHASC) is added on the Jura side of the vacuum vessel to cover the range [+160mm < x < +460mm, -150mm < y <+150mm]] opposite the old HASC, so as also to detect pi- and e- escaping from the beam tube.
K12HIKA+2023, dated 25/07/23, shows the replacement of the CEDAR-N by the specially-built CEDAR-H (XCED101072), filled with hydrogen gas at 3.875 bar working pressure to tag K+ at75 GeV/c. Its entrance and exit windows are 0.15mm and 0.20mm thick Al, respectively. The doubling-up of XWCM101264 and XION101265 is also indicated.

The K12 beam optics for the 2023 data-taking period can be found here.

BEAM SIMULATIONS - TURTLE AND HALO

TURTLE is a ray-tracing programme for in-beam particles, (referred to as "PI" or "KA" in HALO). HALO also tracks muons ("MU"), which, if they have left the nominal beam aperture, are referred to as "HALO"). A TURTLE output corresponding to the 2023 beam is available here. Four earlier HALO outputs exist, one for each parent particle: pi+, K+, pi-, K-. The entries in the corresponding histograms should therefore be summed. The normalization is chosen such that each entry represents a nominal, instantaneous rate of 10 kHz or 1 x 10^4 muons per effective second of spill. An average of 1 entry/cm^2 (= 10^4 muons/cm^2/second) thereby corresponds to an annual dose of ~5 Gy, assuming a year of 100 days of running with an effective duty-cycle of 0.2.