1. 1 TRACK CHAMBERS BASED ON PRECISION DRIFT TUBES HOUSED INSIDE 30 mm MYLAR PIPE A.Borisov, N.Bozhko, R.Fakhrutdinov, A.Kozhin, B.Leontiev, A.Levin

2. 2 IHEP (Protvino) has developed for ATLAS muon spectrometer 30 mm diameter drift tube with 100 mkm resolution. 76 000 tubes arranged into 254 chambers were assembled at Protvino for ATLAS (21% of ATLAS muon spectrometer total). After ATLAS production era, using this technology, about 50 drift chambers were manufactured for the experiments at IHEP 70-Gev accelerator and cosmic ray muon tomography setup.

3. 3 Schematic view of MDT layer Chamber consists of 2 multi-layers, 3 tube layers each Outer tube diameter 30 мм, wall thickness 0.4 мм, made of Al Sense wire 50 mkm W(Re), 350 g tension, 10 mkm positioning Tube length up to 6.3 м. Number of tubes up to 56/layer Glue Araldite 2011 ( AW-106 +Hardener 953 U)

4. 4 а) б) “Event display” (а) и “residuals” (б) cosmic test

5. 5 Chambers of 30-mm Al drift tubes for IHEP FODS (10 psc.), OKA (2 psc.), muon tomography (8 x 24 psc.)

6. 6 MDT ATLAS – very reliable, precise We have experienced staff, tools Developed gas-, RO- and HV-parts of chamber BUT: Some experiments are requiring low-material chambers. ATLAS tube wall is 0.4 mm of aluminium. We have developed drift tube made of lavsan (Mylar)*film with wall thickness 0.125 mm conserving all achievements of ATLAS drif tubes. ---------------------------------------------- * Mylar is trade mark of DuPoint, lavsan – (SU, Лаборатория Высокомолекулярных Соединений Академии Наук), chemical name polyethylene terephthalate

7. 7 Drift tube exploded view

8. 8 Photos of drift tube parts Assembled tube is self supported structure. It keeps round shape and wire tension without external supports and without gas overpressure inside!

9. 9 а) b) c) Raw material - lavsan film – comes in bobbin. Film thickness is 0.125 mm. Both sides are already covered (dusted) with aluminium 0.08 mkm. The film is cut on strips of 100 mm width and length corresponding to the length of drift tube to be assembled. Conductivity of both sides is checked. The side with better conductivity is to be faced inside the tube then. assembled tubes. Distribution of resistance: а) internal surface of strip 2526 мм length; b) outer surface; c) assembled tubes.

10. 10 Ultrasonic welding of lavsan pipe Mylar strip and steel mandrel (bar OD=29.6 mm) are put into the grooves of the ultra sonic welding setup and tightly clamped. Welding head moves along tube axis (V ~ 60 cm/min.) to weld (producing longitudinal joint) overlapped strip sides. Device - “Гиминей-ультра“ АУС-0.2/22-ОМ (Russian name).

11. 11 Weld joint Welding at 90% power of ultrasonic pulser. Contact surface is 2.5x0.8mm2, Load 1.2 kg. Speed 0.6 cm/min. Breaking force of weld joint is 8-10 kg, while plastic deformation of lavsan film starts at about of 15 kg.

12. 12 Tube assembling Wire is sucked by vacuum through the pipe. Then wire is passed through end-plugs manually. End-plugs (their surfaces are covered with glue “Araldite 2011”) are installed into the pipe and tightly fixed to provide electrical contact. Wire is fixed (crimped) at one side. Tube goes to auxiliary stand for the time of glue curing. Wire is stretched (350 g) and fixed (crimped) in the second end-plug.

13. 13 Tension of wire Auxiliary stand in which the tubes are installed for the time of glue curing. Wire tension of assembled tubes is measured by its vibration in magnetic field.

14. 14 High-voltage test Measurement of current against voltage curve for each tube at air at normal conditions. Tubes with abnormal behaviour of the curve are discarded

15. 15 Gas-leak test Drift tube filled with N 2 +10%He at 2 bar(abs) in vacuum box. Fast (2 minutes) check with He- mass-spectrometer. Leak-rate scaled to Ar+CO2 should be below 2∙10 -7 bar∙l/sec for 2.5 m drift tube

16. 16 Cosmic counting rate Al (L=3м) and mylar (L=2м) drift tubes, Ar+7%CO2 at 0.5 bar overpressure without gas exchange: 0,10,41,55,100,150 days.

17. 17 Gluing of chamber module

18. 18 Glued chambers (modules). Different sizes and quantities of tubes in the module.

19. 19 Two chambers in one frame. For OKA setup (IHEP). Tube length 1776 мм 3 layers for X- and Y-projection

20. 20 Electrical connections of single drift tube 1 – amplifier 2,3 – boards with passive (R,C) components, each for 24 (3х8) tubes

21. 21 RO side of the chamber with Farady-cage

22. 22 Gas connections

23. 23 Influence of humidity End plug (NORYL GFN-3) has large water permeability and lavsan film as well. Despite of low gas-leak rate (tubes can work without continuous exchange of working gas mixture) fraction of water inside tube will follow air humidity. Example of maximal drift time in closed tube (Ar+7%CO2 at 0.5)

24. 24 Resolution example Any gas mixture can be used in the tube. Limitations: it must not eliminate (corrosion) Al from the film; working voltage must be below 5 kV (end-plug insulator). Here is example with Ar+7%CO2 at 1.5 bar(abs) and cosmic muons. For the tracks with large number of hits (more 15 hits here) residuals is close to single tube resolution. Residuals distribution was fitted with sum of two Gaussian curves, σ (narrow) is 140-150 mkm.

25. 25Conclusion 1. Precise 30 mm drift tube housed inside the pipe made of mylar (thickness 0.125 mm, both sides are covered with Al) has been developed. 2. Three-layer drift chambers based on such tubes were developed. 3. 26 chambers (dimensions from 0.8x1.0 to 2.5 x2.5 m 2 ) totally consisting of 4440 drift tubes are produced for IHEP experimental setups.

26. 26 Thank you for your attention