1. NA 62 – straw detector Content Detector Specifications Chamber design Straw design and specifications Calculations and measurements Prototyping Plans Straw review 16/9/2009

2. Straw tracker layout 4 chambers 4 views in each chamber 448 (4x112) straws in each view 448x16 = 7168 straws Operate in vacuum 2.1m long D i =9.8mm Precise tracking (<120 μm) Hermetic for tracks -3 degree <  < 3 degree. Minimum diameter is 9.4 mm Straw rate: up to 0.5 MHz Non-flammable gas mixture CO2 (90%)+ CF4 (5%) + Isobutene (5%) 448 (4x112) straws in each view Straw review 16/9/2009

3. Test beam in 2008 Straw review 16/9/2009 The effective radius of the straw is one important component in the straw layout. R effective =4.7 mm

4. Detector assembly Straw review 16/9/2009

5. Straw proto status Straw review 16/9/2009 40 straws out of 64 have been installed I invite you to come to 154 to look at the different prototypes and long term mechanical set-ups

6. Prototype assembly detail of straw installation Straw review 16/9/2009 We test two solutions for straw insertions Key issues: leak tightness & straw straightness)

7. Straw specifications Long term mechanical stability No or little material to limit multiple scattering.  No mechanical supports Withstand 0.5 MHz with CF4 Work in vacuum –Resist to 1 bar over pressure for several years. Straight straws < 200  m (for a hermetic detector) –Support and keep pretension –Spacer every 70 cm Gas tight to minimize pumping power (10 -6 mbar) –Low permeation  protection by metal layer –No leaks (weld and straw fixations) Straw review 16/9/2009

8. Why welded straw Classical winded straw does not work with pretension due to the creep in the joint between the two films (back-to-back gluing). Example: ATLAS TRT, LHC- b, AMS, COMPASS Reinforced straws more material and complicated (ATLAS TRT) Straw review 16/9/2009

9. NA62 straws  We have studied two straws I.32  m Mylar with 200 nm Aluminum coating on both sides II.32  m Mylar with Au/Cu copper coating on one side (200nm/500nm)  Problem with weld was discovered with the CREAM experiment in April. They have 2000 straws made from the same production line. 1% broken straws (in the weld) after 2 weeks and 1 bar overpressure  Permeation looks too high for both straws  Comment: Unfortunately the weld in the straws worked well without problem for the first prototypes (low statistics) Straw review 16/9/2009

10. Pretension straw mechanics Straw review 16/9/2009 Why we have straw deformation in vacuum Solution: pretension with enough margin allowing for creep (horizontal straw):

11. Straw review 16/9/2009 The pressure in the gas (or liquid) adds a bending moment, which has to be taken by the straw wall. Always in compression if  < 0.5Explanation

12. Deformation of the straw as a function of pressure for different pre-tension and pressure Straw review 16/9/2009

13. Long term mechanical tests of the straws (~ 9 months) Long term horizontal tests –Study the sag of the straw over time an and the tension in the straws Long term vertical test. study the elongation of the straw test See Sergei Movchan’s talk for more data (3.5 years)

14. Long term mechanical test results Straw review 16/9/2009 Horizontal straw 1.85 m long. Start: December 2008

15. Straw review 16/9/2009 Long term mechanical test results Absolute deformation of vertical straws (1.2m, 1.5 kg and 1 bar)

16. Conclusion of the mechanical test Adding 1 bar over pressure corresponds to a loss of tension of about 400g –This can be seen in the sag of a horizontal straw or from the frequency measurement We have two supports for the straw, which gives 70 cm between supports Our long term tests indicates some creep but (we believe) acceptably It is important to measure the tension after insertion We have a concluded that with 1.5 kg pretension (1.5 kg/mm 2 ) we will have enough margin to keep the straw straight in tension over several years years Straw review 16/9/2009 Creep (specifications from Dupont) “Mylar® is unusually resistant to creep. Two values measured at room temperature are 0.1% after 260 hr at 2.09 kg/mm2 (2.98 kpsi) and 0.2% after 1000 hr at 2.10 kg/mm2 (3.00 kpsi). After 4000 hr at 0.35 kg/mm2 (0.50 kpsi) in 100°C (212°F) oven, a creep of 0.9% was measured.”

17. QC for series production Tension (frequency) measurement of every straw Straw straightness measurement for every straw plane Straw review 16/9/2009

18. Straw straightness device- results with 1 bar Straw review 16/9/2009

19. QC tension measurement Straw review 16/9/2009 IR emitter and receiver: Tension  w  f 2 where w is the weight per unit length and f the frequency

20. Condition straw after production 1 bar pressure for protection, handling and long term conditioning before final leak test and assembly Straw review 16/9/2009

21. Future Plans Terminate the detailed study on the straw material and its mechanics Build and evaluate design of the 64-straw prototype: –Verify mechanical support of the straws (and wire). Measure final straw deformation and wire off-set. Measure leak tightness Implement new welding and QC procedure (see presentation by Sergei) Aging/etching test of the straw (see separate presentation) Permeation test (separate presentation) Test the new pre-production sample from Fraunhofer (Cu/Au). It should arrive at end of October already cut in rolls Conclude on straw material at the end of 2009 (tight!) Beginning 2010 order the straw material Start straw production in May 2010 Start module-0 assembly in the fall 2010 Straw review 16/9/2009

22. Spares

23. Effects of pressure Straw review 16/9/2009

24. Calculations “water hose” Straw review 16/9/2009