# Presentation: 528592

## LANNDD

*LANNDD*

*A LINE OF LIQUID ARGON TPC DETECTORS*
*SCALABLE IN MASS FROM 200 TONS TO 100 KTONS*
_*David B. Cline*_* 1**, Fabrizio Raffaelli** 2 **and Franco Sergiampietri** 1,2*

*1** Astrophysics Division, Department of Physics & Astronomy,*
*University of California, Los Angeles, CA 90095 USA*
*2** INFN-Sezione di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, ITALY*

## LARGE SIZE LAr TPC CONSTRAINTS AND GENERAL LINES - 1 

*Huge costs, multi-year construction and commissioning: justified only by a credible physics plan that should include** **natural **and **artificial neutrino** **physics and** **nucleon decay** **physics*
*Required: detector siting in** **UG laboratory**,  in the line of existing and future neutrino** **beams** **(**off/in-axis**)*
*Modularity** - From a preliminary study** **1,2** **on modularity and shape, indications on the advantages of a single-module cryostat (relevant advantages in fiducial volume, number of channels, heat input, electric power, ...)*

| 1	F. Sergiampietri, On the possibility to extrapolate liquid argon technology to a super massive detector for a future Neutrino Factory, talk given at NuFACT'01, Tsukuba-Japan, May 2001  |
| --- |
| 2	D.B. Cline, F. Sergiampietri, J.G. Learned, K. McDonald, LANNDD: a massive liquid argon detector for proton decay, supernova and solar neutrino studies, and a neutrino factory detector, Proceedings of NuFACT'01, Tsukuba-Japan, May 2001, NIM A, 503 (2003) 136 |

## CONSTRAINTS AND GENERAL LINES - 2 

*Shapes**: Fiducial-to-active volume ratio, heat input, wall out-gassing, number of wires and electronic channels are related to the surface-to-volume ratio (S/V). *
*A cubic vessel has the same S/V ratio than a cylindrical or spherical one inscribed in it, but with volume ratios*
*                               **V**cube **= 1      V**cyl **= 0.8      V**sph **= 0.5** *

*The **spherical **shape has in principle the highest advantages for the mechanical stiffness but, in practice, can be considered only with a radius equal to the maximum drift path (only one meridian, bi-face wire chamber) *
*The** **cylindrical **shape appears a good compromise between time projection imaging mechanism and required structural stiffness, but with a non optimal ratio between the instrumented LAr volume and the total LAr volume *
*The** **cubic** **(parallelepiped) shape is the most adapt for the projection imaging geometry and for the instrumented-to-total LAr volume ratio, but requires special care in the design for the required mechanical stiffness*

## CONSTRAINTS AND GENERAL LINES - 3 

*Main construction criteria – Construction and Running Costs*
*In a not negligible fraction, **construction costs** depend on the number of wires and associated electronic channels.*
*Roads to follow: *
*Widen the drift region** between each cathode and the facing wire chamber (drift paths up to 5 meters). Operation with such drift lengths implies the use of high voltages in the range 200**~**300 kV and sets serious constraints on the LAr purity (impurities ≤ 10**~**50 ppt O**2** equivalent).*
*New generation electronics**: *
*higher S/N ratio, to balance the long drift attenuation*
*medium scale integration (goal: 2~10 times cheaper)*
*operating in LAr, with front-end directly connected to the wires to avoid the capacitance load of long signal cables*
*multiplexed in LAr, to decrease the number of signal feedthroughs*
*Two read-out wire planes** per chamber (orientation 0° and 90°)*

## CONSTRAINTS AND GENERAL LINES - 4

*In order to reach and maintain during years the required level of purity we consider as inalienable the following construction criteria and conditions:*
*Possibility of generating **vacuum** inside the inner vessel and of checking its tightness*
*Wise choice of **construction materials** (use of stainless steel for the inner vessel walls and for cathodes, for wire chamber frame and for electrical field shaping electrodes; possible use of alternative and cheaper alloys, as CORTEN, for the outer vessel)*
*Continuous, adiabatic argon **purification** in liquid phase*
*UHP and UHV standards** for any device and cryogenic detail (flanges, valves, pipes, welding) in contact with the argon*
*Running costs** are mainly related to the efficiency of the thermal insulation. **Vacuum** insulation, joint to the use of **superinsulation** jacket around the cold vessel, should be considered as the primary choice.*
*An optimized thermal insulation, with a low rate evaporation for LAr and low electric power involvement for cryogenerators, is also a *_*must*_* to **safely** operate the detector underground during tenths of years*

## The LANNDD cellular structure -1

*We have studied a solution that allows a continuous (not segmented) active LAr volume (high fiducial volume) contained in a cryostat based in a multi-cell mechanical structure. This solution allows a cubic shape composed by** **n** 3** **cells, 5m****5m****5m in size each.*

*The cryostat is made by an inner and an outer cubic box** **elastically linked** **in between by thermal bridge beams.*
*The thermal bridge beams are allowed** **to** **slide** **wrt a central point in the basement to compensate the** **thermal shirking** of the inner box.*
*The inner box is fully wrapped by** **superinsulation** **layers.*
*Both the inner and outer boxes have double-face linked walls, to allow a** **sector by sector vacuum tightness check.*
*The lattice beam structure is** **vacuum tight** **as well. The inner beam structure is used for distributed** and uniform **LN**2 **cooling** **by sectors. *

*n = 3*

## The LANNDD cellular structure - 2

*The LANNDD cellular structure - 2*

*The inner cellular structure is a repetitive 3-D array of cubic boxes (**left**) with walls reinforced by double cross beams (**right**). The connection to the outer (warm) wall is obtained by thermal bridge beams, elastically linked at middle length of the cold beams.*

*n = 3*

*THERMAL BRIDGES*

## The LANNDD cellular structure – Rectangular vessel consideration 1

*The design of large rectangular vessel requires special attentions:*
*1)**	**To obtain the right bending stiffness of the plate without using a large quantity of material *
*2)**	**To control the large moment in the corners of the box.*
*3)**	**The size of the cell must be able to avoid instability problems in the compressed part of the plate.*
*4)**	**The welding connection must be able to transfer the shear between and the contribution to the deflection caused by it must be managed.*
*The increase of the bending stiffness can be achieved by spacing the two plates:  *

*In the process of spacing the two skins are one on traction and the other in compression. This makes the stress uniform in each skins. The shear can contribute to the overall deflection:*

## The LANNDD cellular structure – Rectangular vessel consideration 2

*We need to control the instability regions of the structure where there are compressive stresses that caused instability.*

*A model was done using steel beams - size 500X500 mm, 20 mm thick - and the panels are plates that have a 200 mm thickness (equivalent to the situation of the spacing and thickness). *
*The cell size is 5 meter and there is G10 Block to space inner and outer tank.*
*The pressure is .1 Mpa, from outside, on the outer tank and .3 Mpa, from inside, on the internal tank**.*

*Model for 1/4 of the vessel with 3x3x3 cells, beam structure and symmetry boundary conductions*

## The LANNDD cellular structure – Rectangular vessel consideration 3

*Case with only the external pressure (only the vacuum, no internal pressure). Units are in meter Pa. The max displacement is 7.8 mm.*

*Internal and external pressure give the *_*same results*_

*This picture shows the problems that can arise on the corners (some optimization maybe required)*

## Structural tests: LANNDD - 001

*Structural tests: LANNDD - 001*

*A single cell detector is proposed as study prototype to analyze the **mechanical stiffness** of the inbox-outbox complex at room and at low temperature and in condition to simulate a 7bar + 1bar (vacuum) head pressure for the extension to n=8 (LAr depth = 48m).*
*The detector is useful for **developing** and **testing** the HV system, the readout electronics, the purification and cooling systems, the acquisition and reconstruction software and all the **repetitive details** and solutions to adopt for the full scale detector.*
*The instrumented LAr has a volume of **125 m** 3** and a mass of **175 Ton*

*n = 1*

*SUPERINSULATION*

*INNER BOX*

*OUTER BOX*

*FIELD SHAPING ELECTRODES*

*WIRE CHAMBER*

*PM’S*

*HV PS & FEEDTHROUGH*

*CATHODE*

*THERMAL BRIDGES*

## Intermediate Mass: LANNDD - 027

*An intermediate mass detector for use as near detector or in an off-axis** **ν**-**beam line is made by 3**3 **= 27 basic cubic cells. The active volume is split into 3 drift volumes 16x16x5** **m**3**, **with two 0.7 m thick layers in between to host the inner beam structure lattice and photo-multiplier arrays. *
*The instrumented LAr has a volume of **3’834** m** 3** **and a mass of **5.4 kTon*

*n = 3*

## Maximum Mass: LANNDD - 512

*The maximum mass detector for use as far detector in a LBL** **ν**- **beam and for nucleon decay studies in an underground site is made by 8** **3**= 512 basic cubic cells.*
*The instrumented LAr has a volume of** **76’900 m** 3** **and a mass of** **122 kTon*

*n = 8*

*WIRE CHAMBERS*

*HV PS & FEEDTHROUGH*

*CATHODES*

*PM’S*

*SIGNAL ELECTRONICS*

*FIELD SHAPING ELECTRODES*

## SCALING

*SCALING*

| N. of cells/side | 1 | 2 | 3 | 4 | 6 | 8 |
| --- | --- | --- | --- | --- | --- | --- |
| Total N. of cells | 1 | 8 | 27 | 64 | 216 | 512 |
| Total LAr volume [103 m3] | 0.14 | 1.36 | 4.93 | 12.1 | 42.4 | 102 |
| Active LAr volume [103 m3] | 0.14 | 1.27 | 4.49 | 10.9 | 35.9 | 86.9 |
| Active LAr mass [KTon] | 0.19 | 1.78 | 6.28 | 15.2 | 50.3 | 122 |
| Total inner beam length [Km] | 0.08 | 0.34 | 0.89 | 1.83 | 5.37 | 11.8 |
| Total heat input [KW] | 0.3 | 1.0 | 2.1 | 3.7 | 8.1 | 14 |
| Equiv. LN2 consumption [m3/d] | 0.18 | 0.63 | 1.36 | 2.36 | 5.2 | 9.1 |
| Equiv. El. Power-Cooling [KW] | 2.8 | 9.8 | 21 | 37 | 81 | 140 |
| N. of wire chambers | 1 | 2 | 3 | 4 | 24 | 32 |
| N. of channels [103] | 3.3 | 14 | 33 | 59 | 270 | 483 |
| El. Power-Electronics [KW] | 6 | 25 | 57 | 103 | 469 | 839 |

## CONCLUSIONS

*The cubic **shape** optimizes the ratio between active and total LAr volumes and allows a detector made by equal length (and impedance) wires.*
*The proposed **cellular structure** combines mechanical stiffness with large, continuous active LAr volumes. **FEA gives satisfactory indications**.*
*The residual non-active LAr layers due to the inner beam structure are fruitfully used for:*
* **distributed LN**2** cooling*
* **positioning of a **3-D array of photomultipliers** with a complete coverage of the active LAr**. *
*The test and optimization of this solution (and of all the concerned techniques) can be performed on a **single-cell prototype**.*
*Vacuum insulation**,  wise choices for construction materials, UHP & UHV standards for the components assure an exceptionally **cheap and safe** operation for long term running and widely compensate their construction costs.*