4%. The weighted response
of the initial layer(s) of the hadron calorimeter is used separately
applying a correction taking into account the ratio EH1/(EH1+EH2)
.
The endcap hadron calorimeter (HE) covers a rapidity region between 1.3 and 3.0 with good hermiticity, good transverse granularity, moderate energy resolution and a sufficient depth. A lateral granularity ( x ) was chosen 0.087 x 0.087. The hadron calorimeter granularity must match the EM granularity to simplify the trigger.
The basic requirements of the HE design are the following:
- nonmagnetic material for absorber;
- minimal of the absorber to have maximum absorption length;
- total calorimeter length about 10 to provide sufficient containment of high energy jets;
- sampling must be adequate to the required energy resolution;
- minimal dead zones to measure missing energy.
The basic structure of the endcap calorimeter is the same as for the barrel calorimeter. A crystal electromagnetic calorimeter (EE) of 27 X0 is placed in front of HE. The total depth of the HE calorimeter (not counting the electromagnetic calorimeter) is about 10 absorption lengths (19 active layers). The absorber sampling thickness is 8 cm. The absorber material is brass (90% Cu+10% Zn), the front and back plates are made of stainless steel to increase strength. The absorber plates are bolted together to form a single monolithic structure, with gaps for scintillator insertion. This structure is conceptually similar to the barrel structure, although differing in engineering details because of the endcap geometry and mounting scheme. The entire HE monolith is fastened from its back stainless steel plate to a 10.0 cm front plate of the Endcap Muon absorber steel (YE1).
The EE electromagnetic calorimeter is attached to the front face
stainless steel plate of HE (1.16 times thicker than the brass
plate for an interaction length equivalent to that of the brass
absorber). The total thickness of the front plate is determined
by the dead material introduced by EE cables, electronics etc.
(about 0.1 ). So the thickness of the plate may be reduced by
this amount in order not to introduce additional layer
of scintillators. The EE is a highly non-compensating calorimeter
that introduces nonlinearity of energy response and degrades the
energy resolution. To correct these effects in some degree a weighting
technique may be used. In this case the expected energy resolution
is E/E = 105%/ 4%. The weighted response
of the initial layer(s) of the hadron calorimeter is used separately
applying a correction taking into account the ratio EH1/(EH1+EH2)
.
Each end cap is an 18 sided polyhedron that covers and closes one end of the barrel calorimeter. The HE is constructed of plates, separated by staggered spacers, that are perpendicular to the beam axis. The basic geometrical parameters of the HE are shown in Fig. 3.1.
Fig. 3.1: Scintillating plates are mounted on aluminum plates forming trapezoidal tray ("pizza pan") structures which are installed in the gaps of the endcap absorber. The construction allows easy access to the pizza pans and provides a rigid structure.
The basic design guidelines are:
- the absorber must be made of brass plates with minimal gaps ( 0.5 mm) in ;
- mechanical assemblage of the absorber plates with bolts ;
- design must provide for the required insertion of megatiles and easy removal;
- back flange is made of stainless steel;
- dimensions of the absorber plates in f must correspond to minimal cost, minimal waste and maximum machinability;
- absorber design and all interface elements must satisfy the safety requirements to sustain about 300 tonnes and provide stable position of endcap in space during all operation time;
- safe operation during access to EE and HE and to the interior of the detector;
- provide the required precision of muon chambers ME1 alignment, with the possibility to replace separate chambers without interfering with other end cap systems;
- HE design and the interface zone must correspond to the requirements of the standard assembling procedures and time schedule at the CERN assembly hall on the surface;
- the cost must be within the allocated sum;
- the safety factor for the most loaded elements (taking into account all combined stresses) must be greater than 2;
- the calculations of stresses and deformations must take into account dynamical forces equal to 0.15g.
The endcap hadron calorimeter covers the rapidity region between 1.3 and 3.0 and is an 18 sided polyhedron in shape. The HE consists of the absorber plates with 19 sampling gaps filled with scintillator trays. The scintillator response signal is transferred via optical cables to megatiles decoder boxes in which the signals from tiles forming a single ( x f) tower are optically mixed together. The decoder box also contains the readout photodetectors, the frontend amplifiers, as well as the initial signal digitizers. This figure shows a cut through the vertical plane of the HE cross section in y-z plane. Fig. 3.2 presents the endcap segmentation (HE and EE) in f and Fig. 3.3 shows the longitudinal structure of HE.
The HE design with mechanical connection of elements is presented in Fig. 3.4. Absorber elements and spacers are connected with bolts M24x2 with cylindrical head. To eliminate a relative shift of absorber elements in the vertical plane under the shear forces due to the HE weight, a large number of collets with diameter 36mm are used for interplate connection and stabilization.
The calorimeter is formed by assemblage of sector and spacer elements. Each layer consists of 180 brass sectors 35 mm thick. The sector layers are separated by 18 brass spacers 9 mm thick covering 100 in f for the scintillator insertion gaps.
From the production point of view the following requirements were taken into account:
- to cut the cost of the absorber plates produced by industry the sector plate cover 200 in f;
- minimization of the absorber plate dimensions allows to use standard industrial equipment with required precision of machining;
- to control the quality of all industrially produced absorber elements a control assemblage is planed;
- an analysis of sector absorber production from rolled plates with width 600, 1060, 1200, 1250 and 1500 mm shows that the most economical option is 200 sectors;
- several producers of rolled plates were considered: Bulgaria (produces plates up to 1060 mm wide); Orsk plant OTM, Russia (produces plates up to 1200 mm wide); "Krasnyi Vyborzhets" plant in St.Petersburg, Russia (produces plates up to 1500 mm wide); metallurgical plant in Bendzin, Poland; KGHM Poland copper; firm "Outukumna", Finland.
The HE absorber consists of alternating layers of sector and spacer plates connected with bolts and collets (see Fig. 3.5). The arrangement of the even and odd layers is shown in Fig. 3.6. The numbering of the layers starts from the layer closest to the interaction point and is shown in Fig. 3.7. The layer numbering scheme is the same as that in the barrel, namely that the layer immediately following the innermost stainless steel plate is numbered as layer one, while the layer following the outermost stainless steel plate is layer 19. Plates in front of the innermost stainless steel plate of HE will be numbered zero (and -1). The geometry of the sector and the spacer is presented in Fig. 3.8.
All absorber plates are connected with bolts and collets. The general layout is shown in Fig. 3.5. The collet design is shown in Fig. 3.9, while Fig. 3.10 presents the bolted connection.
The number of fastening elements along the z-axis (HE depth) is optimized (see Fig. 3.11). The most loaded layer # 38 (next to the back flange) has 468 bolts M24x2, the less loaded layer #1 has 216 bolts. The number of collets with diameter 36 mm and cross section 756 mm2 is 72 in the last layer. The layers assemblage is made with torque indication wrench that allows to increase static load on the bolts by a factor of 2.
The input data for the calculations are:
- the schematic location of the center of gravity and weight of the endcap components including the endcap crystal EE and its mounting frame (Fig. 3.12);
- the material of the bolts, nuts and collets is brass (yield limit equals to 2.94x102 MPa);
- the sector material is brass;
- the bolt and collet dimensions are presented in Figs. 3.9 and 3.10.
The rating scheme is based on the layout presented in Fig. 3.13. The calculation results of the stress values and the safety factor are presented in Fig. 3.14.
The absorber material and construction elements (bolts and nuts) were tested with a machine made by Instron. The machine could develop a force of up to 20 tonnes. The main results of this testing are the following:
1. Force for the beginning of the plastic deformation for M24*2 bronze BrX1 bolt Fpl = 14.2 tonnes. That is much more than the required load Fa = 5767 kg.
2. The bolt elongation before bolt break down = 6 mm (15% of length).
3. Force for break down of bolt thread = 16 tonnes.
4. Force for break down of absorber material (for copper) under bolt head surface = 17.5 tonnes. For brass, the required force is 1.5 to 2 times more.
Thus the materials (brass for absorber and bronze for connecting
elements) meet all requirements.
The layout of the HE collets is shown in Fig. 3.15. The calculation results of the stresses and safety factors are presented in Fig. 3.16.
The ANSYS finite element program was used to model the HE for
the purposes of determining bolt loads, plate stresses, and deflections
under normal static operational conditions. This model is shown
in Fig. 3.17. Eight node solid elements modeled all components,
and a total of 80 k nodes and 40 k elements were used in the model.
The entire HE, with the exception of the backflange and inner ring, is made of discreet 20 degree sector and spacer plate segments. The segments are connected to each other by 24 mm diameter bronze bolts and collets. The backflange and inner ring are 360 degree annuli.
Fig. 3.18 is a close-up of a typical sector/spacer plate connection. Because the spacer plates are through bolted to the sector plates, and the sector plates stagger azimuthally by twenty degrees between each layer, the load path is a zig-zag through the plates in z, and the bronze bolts and collets are responsible for transmitting the forces back to the support points. The modeling of this load path in precise detail is impossible given the large problem size which results. Instead, the "bolts" were represented by spring elements along the radial edges of the sector/spacer plate junctions. Although the actual bolt will pass through two sector plates and sandwich the intermediate spacer plate, the finite element model places "bolts" only at one of the sector/spacer interfaces; the other interface is merged into a continuous line. This will not change the calculated bolt loads, since the load at each merged interface must pass through a spring-simulated "bolt" to reach the support points.
The collets, which serve a shear function only, were modeled at the same points as the bolts by applying two additional spring elements acting in the radial and azimuthal directions.
The number of spring elements on a radial connection line does not represent the exact number of bolts in each sector. There are a minimum of 13 bolts along each radial bolting line at the most heavily loaded locations; the model uses 11 bolts along every line, except near the support, where 10 are used. The force output from the program was taken at face value to represent a single bolt, with the resulting conservatism ignored.
The stiffness of the bolted joint, which is input to the model as the stiffness of the springs, was estimated with a 2-d axisymmetric model of a typical joint.The bolt was modeled as brass, 24 mm in diameter, and the recessed holes for bolt head and nut were included in the model. The bolt was thermally preloaded to 90% of the 300 MPa yield strength of the bolt material, and a load applied to the joint which acted to separated the bolted components. The resulting deflection was used to calculate the bolt stiffness input to the 3-d finite element model. This stiffness was 1.46x106 N/mm.
Stiffness for the spring elements representing the collets, and resisting only shear forces, was set at an arbitrary 1x106 N/mm.
The HE is supported from the endcap iron plate YN1. Three HE steel
components are responsible for this support. The 100 mm thick
backflange is attached at its inner radius to the inner ring (IR)
, which keys and bolts to YN1. The backflange is attached at its
outer radius to the FF plates, which have had substantial material
removed to allow access to the MF1 chambers. In the actual structure,
vertical shear is taken entirely by the connection of the inner
ring to YN1. This was simuated by constraining the vertical motion
of the end of the ring. Overturning moment is taken by the FF
plates, which are radially bolted into YN1. This was simulated
by constraining the z-motion of the ends of the stirrup plates.
The EE, which has a mass of 10000 kg, bolts to the upstream end of the HE. This mass loading was simulated by using a point mass element located at a z (relative to the i.p.) of 3365 mm. The mass element was supported from the upstream end of HE by two massless and very stiff spar elements. Therefore, while the details of the support effects on the upstream end of HE are not precisely modeled, they are almost certainly simulated in a way which will increase the local loading on HE, and produce the correct mass and moment effects.
Working stresses for the bolts and collets were taken as 2/3 of the 300 MPa yield strength for bolt tension or 200 MPa, and 1/3 of 300 MPa for both bolt and collet shear stress, or 100 MPa.
Establishing working stresses in the copper is problematic, as the current specification states only that the ultimate tensile strength is 200 MPa. If the procedures of the ASME Boiler and Pressure Vessel Code, Section VIII, Div. II, Appendix 4, are applied, then the maximum allowable membrane stress is 1/3 of the ultimate, or 66 MPa, and the maximum allowable stress for combined membrane plus bending is 1/2 ultimate, or 100 MPa.
Bearing stresses in the copper at the bolted joint are allowed to reach 3/4 of the ultimate stress, or 150 MPa.
The working stress of the stainless steel of the backflange, inner ring, and stirrup plates were taken as 138 MPa. This value is for SA-240 SS304 stainless steel as specified in the ASME Boiler and Pressure Vessel Code, Section VIII, Div. II.
The loads considered in this analysis were dead weight and earthquake/handling accelerations of 0.15 g. They were applied in the following load cases:
- Dead weight plus 0.15g additional downward force for earthquake/handling.
- Dead weight plus 0.15 g additional force parallel to beam axis for earthquake/handling.
The azimuthally symmetric geometry means that earthquake forces acting horizontally and perpendicular to the beam axis can produce bolt stresses and support reaction which are not higher than those from load case 1. Therefore, the one-half symmetric model is adequate to consider all earthquake effects.
Fig. 3.19 and 3.20 shows the deformed shape of the HE for load cases 1 and 2, respectively. The maximum deflection calculated by the model was at the mass element representing the EE. This deflection was 1.3 mm. This deflection is relative to the stirrup plate and inner ring supports, and does not include any deflection in the YN1 plate.
The bolt tensile stress for both load cases was obtained by dividing the spring force calculated at each "bolt" location by 354 mm2, the tensile stress area of a 24 mm diameter bolt. The maximum tensile bolt stress calculated by this means was 198 MPa for load case 1, and occurs at layer 38, nearest the supports. This is consistent with the location of the maximum cantilever moment. The maximum tensile stress is below the allowable of 200 MPa, and does not take into account that there are actually 13 bolts along a radial line, and not the 10 "bolts" modeled along the line in the finite element model in this most highly loaded region.
Shear stresses, which are taken in the HE by both the bolts and collets, were evaluated with the finite element model by assessing the vertical shear force distribution in the model, and applying the forces to the actual bolt and collet areas available. This was done at the most highly sheared location, which is layer 38. The cross section was divided into ten horizontal strips, and the shear force calculated. The most heavily sheared regions are at the top and bottom of the circular area, which each see a shear force of 7.24x105 N over an area of 14.22 x 105 mm2, or an average shear (if the spacer and sector plates were continuously connected) of 0.51 MPa. The area available for shear from the bolts is the number of bolts in the layer times the bolt stress area, or 468 x 353.87 = 1.66x105 mm2. The total area of the layer is 1x107 mm2. Scaling by the ratio 100/1.66, the average shear stress on the bolts in these most highly stressed regions is 31 MPa. This is well below the allowable of 70 MPa, and neglects the contribution of the collets.
The copper from which the sector and spacer plates are made is softer than the brass bolts, having an ultimate strength of 200 MPa. This material must take the bearing stress produced by bolt preload and external loading. A calculation of the bearing stress under the bolt head due to preload can be made by applying the preload force to the bearing area. For a preload of 270 MPa and a bolt stress area of 353.87 mm2, a force of 9.55x104 N is required. If the contact area at the bolt head is 680 mm2, the resultant average bearing stress on the copper under the bolt head is 140 MPa. This is below the ultimate strength of the copper material.
Bearing in the hole resulting from shear can be calculated by taking the average shear force per bolt calculated above and applying it to the bearing area of the hole. If the hole against which the bolt shank bears is 31 mm long and 24 mm in diameter, the projected bearing area is 372 mm2 (for single shear) For a shear force of 51 x 353.87 = 1.8x104 N, the resultant bearing is 48 MPa. This is below the ultimate strength of the copper material.
The 2-d finite element bolting model, which was used to find the stiffness of the joint for input to the spring elements in the 3-d model, can also be used to look at the actual distribution of external force between the bolt and the clamped materials. The purpose of preloading is to stiffen the joint by compressing the material, and ensuring that its compliance is a part of overall joint behavior. Fig. 3.21 shows the joint, preloaded to 270 MPa, with an external force of 70 kN applied as a shear at the outer boundary of the top sector plate. The results show that the axial bolt stress, averaged over the bolt area, increases from 270 MPa to 280 MPa under this load. Though this loading method is a simplification of the actual 3-dimensional load path, the results show that the preloaded joint effectively involves the clamped materials in its overall load response.
The maximum membrane stress in the copper is 48 MPa for load case 1, and occurs at a bolted spacer/sector plate junction in layer 38. At this same location, the maximum membrane plus bending stress is 68 MPa. Both of these stresses are below those allowable established from the specified ultimate tensile strength.
The stresses in the back flange, stirrup plates, and inner ring are shown in Fig. 3.22 for load case 1. The maximum stress is 65 MPa, which is well below the allowable of 138 MPa.
The bolted sector/spacer plate connection has sufficient strength to allow support of the HE from the stirrup plates and inner ring attached to YE-1, for the condition of dead weight plus 0.15 g vertical or horizontal earthquake or handling accelerations. This analysis shows that both the shear and tension bolt loads are well within the capacity of the design. The collets were not explicitly considered, and any additional shear capability resulting from the material clamping friction was also neglected. The tensile bolt loads were calculated using 20 bolts per sector at layer 38, rather than the 26 called for in the design. Shear stress was calculated by extracting shear distributions from the model and applying them to the actual number of bolts in the design.
The 2-d joint study show that the properly preloaded joint will allow external load sharing between the clamped materials and bolt. Bearing stresses in the joint, when averaged over the available bearing area, are below the working stress limits in bearing for the copper material.
Fig. 3.21 (see also C.S.): Joint preloaded to 270 MPa, with an external force of 70 kN applied as a shear at the outer boundary of the top sector plate.
In case of emergency switch off of the superconducting magnet a drop of the magnetic field from 4 T to zero magnetic field can occur. The changing magnetic field will lead to eddy currents in the endcap which will increase the electromagnetic forces in the HE absorber and as a consequence to additional load on the bolted joints. To minimize (eliminate) such forces the sector and spacer elements have a two layer electrical isolation to minimize (prevent) current flow. The first layer is an oxide layer on the absorber, while the second one is an enamel covering.
Bolt, nut, pin, sector and spacer(collet) material is brass L90 (density is 8.78 g/cm2, ultimate strength is 2.4x102 MPa, yield limit is 1.2x102 MPa, ultimate strength is 2x102 MPa, Brinel hardness (HB) is 50 units, relative extension is 45%).
Brass L90: Cu - 89.5%, Zn - 10%, admixture - 0.5%.
- Nonflatness - 0.5 mm per 1 m.
- Roughness - Rz 6.3.
- Thickness tolerance: 35 +0, -0.5 mm; 9 + 0, -0.2 mm.
Production of HE copper plates has the following steps:
- hot rolling of plates and machining of the sector parts (thickness, contour);
- hole drilling for bolts and pins, the distances between the holes are based on calculation of temperature variation in fabrication shop relative 200 C;
- machining of the spacer contour;
- drilling of the holes for bolts and pins;
- fitting of the coordinate holes;
- checking and documenting of the sectors and spacers;
- machining, checking and assembly of the HE back flange;
- machining, checking and documenting of the fastening elements of HE;
- control assembly and inspection of the HE absorber including the support ring for EE installation (at a factory);
The procedure has been agreed with engineers of the machinery plant which will make the absorber.
The control is realized in to two steps. The first steps is the control of the sector and spacer plates obtained from producer. It includes the control of technical documentation, markers of elements, surface quality, dimensions of plates, mechanical and chemical analysis of the material,
The technical standards of input control are the following:
- technical requirements, quality certificate for the consignment of brass;
- control of plate markers, stamps of the producer in accordance with technical documentation: brands of brass, consignment number, melt and rolled good numbers, stamp of quality control service;
- surface quality control of plates - visual control to check the absence of cracks, grooves and hollows up to 0.5 mm deep;
- dimension control of plates (measurement precision is 1 mm) according to Euronorm standards;
- chemical analysis of brass, the deviation must be within the range mentioned above;
- mechanical control according Euronorm standards, deviation must be within the range mentioned above.
The second step (after production of all HE elements) includes the control of dimensions, machining quality, quality of protective cover according to the technical documentation for all absorber elements (sectors, spacers, flanges). After production each sector and spacer must have a marker with layer number and f position.
Quality assurance is provided by way of technical control at all production stages, metrological attestation of the used apparatus and by calibration of the measuring devices according to methods of Euronorm standards.
All parameters of machining (precision, surface roughness, tolerances on thread holes etc.) are controlled in accordance to Euronorm standards.
A quality certificate of the manufacturing firm must accompany all the components with the following information:
- assortment certificate copy;
- item dimensions with accuracy not worse than 14 quality;
- signature and stamp of technical inspection division leader.
A quality certificate must be drawn up for the check assembly with a purchaser representative attendance.
Quality certificate shall be drawn up after the check assembly has been done and sent to the purchaser with the components in one parcel. The manufacture must have all the certificate copies kept for three years.
The Endcap calorimeter HE will be preassembled at the factory with the goal of the technological development of the absorber assembly, quality control of the produced absorber elements, correction of the mistakes made during previous production stages.
Preassembly is realized on the factory floor (at the nominal factory) which can carry weight above 30 tonnes/m2, the total absorber mass is about 290 tonnes. A crane with carrying capacity 10-15 tonnes must be used.
The assembly set includes two half disks 100 mm thick of the back flange, 6684 sectors 35 mm thick, 684 spacers 9 mm thick, a set of 13824 bolt joinings, a set of 2500 collet joinings.
The control scheme consists of nut pressing into the holes of the back flange half disks, back flange assemblage, pressing of the M24 nuts into sector holes, assemblage of the first layer of the absorber installing 18 spacers and 18 sectors, mounting bolts and collets, fixation of the bolts with torque indication wrench (the force is 4000 kg), assemblage of the second layer and so on up to the last absorber layer, assemblage, positioning and fastening of the centering ring to joint EE, the control of the assembled absorber, disassemblage of the absorber and the back flange, painting of the sectors and spacers, control of the painting, packing and control of the packing, transportation of the absorber elements to CERN (according to Euronorm standards).
An Endcap sector prototype will be designed and constructed before the HE design is finalized. The prototype consists of a full scale sector covering 300 in f equipped with 38 megatiles and 2 decoder boxes including laser and radioactive source control. It's production and assemblage is planed to be completed at the second part of 1997 year. The results of the assemblage will be used to finalize the requirements of the absorber design. The design of the prototype is shown in Fig. 3.23.
The design of the interface support system is shown in Fig. 3.24 and 3.25. It consists of the following elements:
- stainless steel internal support ring (see Fig 3.26);
- back flange disk 100 mm thick made of low carbon steel (see Fig. 3.27);
- intermediate disk 70 mm thick made of aluminum alloy D16T;
- 18 fastening frames made of stainless steel and placed around the outer surface the interface zone (see Fig. 3.28).
An internal support ring is connected to the back flange of HE (see Fig. 3.29) by 18 bolts M36. The fastening frames are fastened to the back flange by 18 keys with dimensions 40x40x210 mm, from the other side it is connected to the flange of nose YE1 by 18 keys with dimensions 80x80x250 mm.
Muon chambers ME1 are placed and positioned on the internal disk with 200 intervals in f. On the outer surface of the internal ring, on the lateral side of the back flange and on the flange disk of nose YE1 a polyethylene radiation protection is placed. On the back surface of the back flange resistive plate chambers (RPC) are set. The layout of the first layer of muon chambers is shown in Fig. 3.29. The design of the 100 mm back flange disk is presented in Fig. 3.30.
The proposed design of the interface zone must satisfy the following requirements:
- stable spatial position of endcap calorimeters;
- ensure the pre-determined spatial position of ME1;
- assemblage and disassemblage of ME1 and the RPC system without destruction of the mechanical structural elements;
- optimal cable and cooling system laying;
- place for polyethylene radiation protection;
- assemblage and disassemblage of all endcap calorimeters.
The basic fastening elements have been enumerated above. To prevent the collapse and/or deformation of the back flange from the 100 mm YE1 nose under electromagnetic force the back flange is fastened with 37 bolts M24x2 to the YN1 disk 240mm thick.
The input data are shown in Fig. 3.12. The materials used for the calculations are:
- material of the key (Figs. 3.30 and 3.31) is steel 40x13, steel 20;
- material of the bolt (Fig. 3.32) is steel 65G;
- material of the top bracket (fastening frame) is stainless steel 12x18H10T (Fig. 3.33).
The results of the stresses and safety factors are presented in Figs. 3.30 - 32. The top bracket maximum deformation is shown in Fig. 3.33.
To position HE and EE a centering support ring is placed on the HE forward absorber plate. The ring is made of stainless steel 08X18H10T. On the outer surface of the support ring EE is fastened by 18 bolts M24 (see Fig. 3.34). The centering support ring is shown in Fig. 3.35.
At CERN in the surface assembly hall HE, ME1, RPC, back flange disk (ED) and disk of the nose YE1 are assembled as a single block and then they are connected to YE1 nose. The assemblage is carried out in horizontal position with subsequent turn of the block on 900 and connection to YE1. Then it is lowered in the experimental hall where EE and preshower are mounted on HE and form a single unit.
The scenario of the assemblage is the following:
- in the surface hall a platform shown in Fig.3.36 is mounted from concrete blocks 5200 mm high and with cross section 7 x7.4 m2;
- 4 technological supports shown in Fig. 3.37 with small hydraulic jacks are installed on the top of the platform (see Fig. 3.38);
- the disk YN1 shown in Fig. 3.39 (weight is 40 tonne and thickness is 240 mm with special cuts to fasten rotational tooling ) is installed on the technological supports using arm presented in Fig. 3.40;
- Fig. 3.41 shows the disk ED ( weight is 18 tonne and thickness is100 mm) installation on the surface of the YN1 disk (fastened by 37 bolts M36x4);
- internal support ring IR ( weight is 5 tonne) is mounted on YN1 (see Fig. 3.42) and positioned by pins M48;
- the bearing base (BB) shown in Fig. 3.43 is mounted on the surface of the disk ED;
- Fig. 3.44 shows the intermediate disk (MD) with 36 steering plates for ME1 and Fig. 3.45 shows MD mounting and fastening using the temporary support shown in Fig. 3.46;
- assemblage of RPC on the HE back flange;
- the back flange (weight is 17 tonne) is mounted on the landing surface of the internal support ring (see Fig. 3.47);
- Eighteen fastening frames are mounted along the perimeter of the interface zone and bolted by torque indication wrench (see Fig. 3.48);
- Fig. 3.49 shows HE absorber assembly;
- Fig. 3.50 shows installation and assembly of scintillator trays with optical and quartz cables and radioactive source tubes;
- installation and assembly of the decoding boxes;
- testing of the control systems;
- installations, alignment and testing of 36 ME1 chambers;
- Fig. 3.51 shows installation of a frame (see Fig. 3.52) on the top of HE and fastening of two plates (see Fig. 3.53) to the disk YN1 and to the frame plates;
- installation of supports for rotation shown in Fig. 3.54 is made in two steps: 1) lifting of the assembled system with hydraulic jacks and 2) installation of supports;
- the whole structure with the support is presented in Fig. 3.55;
- Fig. 3.56 shows rotation of endcap calorimeter on 900;
- Fig. 3.57 shows installation of hydraulic jacks for endcap aliment;
- Fig. 3.58 shows moving of YE1 to endcap;
- connection of YE1 and endcap with stud-bolts and super-nuts is shown in Fig. 3.59, the rotation support is removed;
- YE1 and end cap is moved to the pit and lowered into the hall;
- EE installation and assembly with cables and cooling pipes;
- preshower installation and assembly of cables and cooling pipes, Fig. 3.60 shows the final assemblage.
The preliminary assemblage of the endcaps consists of two stages: preassembly of the HE absorber and preassembly of the interface support structure. The first stage has been described in chapter 3.3.5.2, the interface support structure assembly is presented in chapter 3.5.1.
For mounting and assemblage special handling fixtures described in chapter 3.5.1 will be designed and produced. Standard vacuum lifters (two pad litters) will be used for absorber assembly (sector mounting, 400 tonne). The final assembly of the end caps (HE + EE + preshower + ME1 zone) will be carried out on the vertical supports with 4 hydraulic jacks. To turn the end caps on 900 2 rotational supports will be designed and produced. To connect the end cap calorimeters to YE1 nose 2 special transport blocks will be used.
The full access to the endcaps (EE, HE, RPC and ME1) is possible
only during a long shut down of LHC operation. During this time
all repair work must be done including the replacement of radiation
damaged scintillators. The radioactive source tube control system
will be used to check the performance of the active elements.
For such access, the endcap muon absorber with the attached YE1
disks is moved 10m along the z-axis from the IP. Because the endcaps
are at large height above the Experimental Hall floor (the distance
between the floor and beam height is 8m) service space trusses
must be used for access to the HE and the rest of the Endcap system.
3.1. OVERVIEW AND REQUIREMENTS 1753.1.1 Overview 1753.1.2 Engineering design requirements 1763.2 HE ABSORBER GEOMETRY 1763.3 HE ABSORBER DESIGN AND MANUFACTURE 1783.3.1 Sector and spacer layout 1793.3.2 Fastening elements of HE 1813.3.3 Forces, stress, deflection 1833.3.4 Finite element analysis of HE 1873.3.5 Materials 1943.3.6 Manufacturing procedures 1953.3.7 Absorber prototype 1963.4 INTERFACE OF HE AND THE ENDCAP MUON SYSTEM 1973.4.1 HE and ME interface 1973.4.2 General requirements 2013.4.3 Fastening elements 2013.4.4 Forces, stresses, deflections 2023.4.5 Interface of HE and EE. 2043.5 ENDCAP CALORIMETER ASSEMBLY 2053.5.1 Assembly scenario 2053.5.2 Factory preassembly 2313.5.3 Facilities requirements (CERN assembly hall) 2313.5.4 Tooling design 2313.6 ACCESS, MAINTENANCE AND OPERATION 231