1. 03.06.2015IHEP,Protvino,Russia 1 Current status of a gas luminosity monitor Sergei Erin † † For the LCAL group V.Bezzubov,S.Erin, A.Ferapontov, Yu.Gilitsky,V.Korablev, M.Lobanov, A.Rybin,V. Suzdalev, K.Suzdalev

2. 03.06.2015 IHEP,Protvino,Russia 2 Requirements to luminosity monitor Dynamic luminosity range 10 30 ?-10 34 cm -2 s -1 with reasonable integration time. Bandwidth ~ 10 MHz to resolve luminosity of individual bunches. Improve energy flow measurement in forward/backward direction. High radiation hardness ~ 10 MGy/year and etc. [1]

3. 03.06.2015 IHEP,Protvino,Russia 3 Choice of detector One of number options is a gas ionization calorimeter filled with C 3 F 8. Extensive studies of gas ionization calorimeters have been performed in the last decade[2]. It has been experimentally proved that hadrons/electromagnetic gas calorimeters posses a number of attractive features like good energy resolution, high uniformity and stability, simple calibration and high intrinsic radiation hardness at low cost. Using gas C 3 F 8 one can achieve a good energy resolution and rather low equivalent noise energy even at atmospheric pressure [3].

4. 03.06.2015 IHEP,Protvino,Russia 4 Properties of C3F8 Density  =0.0075 g/cm3 Molecular weight 188 Drift velocity V=0.07mm/ns at ~800V/atm.

5. 03.06.2015 IHEP,Protvino,Russia 5 Properties of C 3 F 8 C 3 F 8 is a gas with electronegative properties  -attachment coefficient  -Townsend coefficient  and  coefficients as a function of electric field

6. 03.06.2015 IHEP,Protvino,Russia 6 Properties of C 3 F 8

7. 03.06.2015 IHEP,Protvino,Russia 7 Previous tests and results Systematic studies of a gas EM calorimeter with 3 and 1.5 mm thick lead absorbers have been performed using electron beams of the 70 GeV IHEP accelerator. Heavy freon C 3 F 8 at pressure up to 1.8 atm. was used as a working gas. The equivalent noise energies for the calorimeter tower are equal to 150 and 180 MeV for the fine and course calorimeter structures at 1 atm. gas pressure. The energy resolution for two types of calorimeter are presented on this fig. It depends weakly on the gas pressure above 0.9 atm. and HV above 600 V. The constant terms are compatible with zero. These are the best characteristics achieved so far for gas ionization calorimeters. [4]

8. 03.06.2015 IHEP,Protvino,Russia 8 Previous tests and results

9. 03.06.2015 IHEP,Protvino,Russia 9 Previous tests and results

10. 03.06.2015 IHEP,Protvino,Russia 10 Previous tests and results So the prototype looks. The thickness of Pb- absorbers is of 3 mm and the thickness of gas bigap is 10mm. On the back side of the gas vessel one can see the readout connectors.

11. 03.06.2015 IHEP,Protvino,Russia 11 Previous tests and results On this photo one can see PCB and absorber for one module of the calorimeter

12. 03.06.2015 IHEP,Protvino,Russia 12 Previous tests and results On this photo are presented one module of gas calorimeter

13. 03.06.2015 IHEP,Protvino,Russia 13 Previous tests and results

14. 03.06.2015 IHEP,Protvino,Russia 14 Previous tests and results On this two photos one can see a procedure of assembling for gas calorimeter

15. 03.06.2015 IHEP,Protvino,Russia 15 Luminosity monitor design The monitor consist of W- absorber plates and the volume between the absorber plates is filled a gas C 3 F 8 with overpressure 0.5 atm. The sensor volume between the two absorber plates contains a PCB layers with a pad structure. The absorber plates are grounded and PCB with pads structure on both sides is on high voltage.

16. 03.06.2015 IHEP,Protvino,Russia 16 Luminosity monitor design

17. 03.06.2015 IHEP,Protvino,Russia 17 MC simulations of luminosity monitor The MC results were received with Geant 3.21 and BRAMS. The energy resolution of gas monitor for different angles of projectiles one can see on the next figures. This results were obtained with Geant.

18. 03.06.2015 IHEP,Protvino,Russia 18 MC simulations of luminosity monitor

19. 03.06.2015 IHEP,Protvino,Russia 19 MC simulations of luminosity monitor

20. 03.06.2015 IHEP,Protvino,Russia 20 Relative measurement of luminosity The measurement of the current of the gas ionization will be used for this purpose. This measurement is available for beam steering. The precision expected is about 1%

21. 03.06.2015 IHEP,Protvino,Russia 21 Relative measurement of luminosity The total current from a calorimeter for electron with E=26 GeV and beam intensity 10 3. This current was measured for the calorimeter with 3mm thick absorbers.

22. 03.06.2015 IHEP,Protvino,Russia 22 The control of gas purity These measurements were carried out with proportional counter working in ionization mode. The current was measured with Kethley 619.

23. 03.06.2015 IHEP,Protvino,Russia 23 Radiation damage We yet did not spend own measurements of radiation damage. Therefore I shall bring the data received in [8]. Small (<10cm 2 ) static liquid C 6 F 14 was irradiated up to 3*10 13 fast neutrons.cm 2. Studies showed the long- lived radioisotope F 18 (106 min.,511 KeV  -emitter). For instantaneous rate of neutron about 10 6 neutrons cm - 2 s -1 the expected level of activity is in the range 10 4 -10 5 Bq.g -1.

24. 03.06.2015 IHEP,Protvino,Russia 24 Radiation damage Small (<10cm 2 ) static liquid C 6 F 14 was exposed to Co 60 gamma irradiation. After an absorbed dose of 6 Mrad surfaces of aluminum and stainless steel samples immersed in liquid C 6 F 14 were covered with a polymeric layer of 0.4  m. The reasons are the impurities containing C-H groups.

25. 03.06.2015 IHEP,Protvino,Russia 25 Radiation damage Conclusions: Density of a gas is less than a density of liquid in 10 3 times. Therefore we can expect that up to 5- 6 Grad we shall not observe the signal degradation from radiation damage.

26. 03.06.2015 IHEP,Protvino,Russia 26 Future plans December 2003 – test beam run Continue MC simulations of luminosity monitor Study of gas properties like drift velocity, attachment coefficient. MC simulation of gas properties with Magboltz ( S.Biagi kindly modified his program for C 3 F 8 ). Mechanical design of luminosity monitor

27. 03.06.2015 IHEP,Protvino,Russia 27 References 1. TESLA-Detector:Instrumentation of the very forward region 2. S.Denisov, et al., Nucl.Instr. And Meth. A 335(1993)106 3. S.R.Hunter, et al., Phys.Rev. A38(1988)58 4. S.Denisov, et al., Nucl.Instr. And Meth. A 419(1998)590 5. S.Denisov, et al., Nucl.Instr. And Meth. A 494(2002)369 6. S.Denisov, et al., presented at the IMAGING 2003, INTERNATIONAL CONFERENCE ON IMAGING TECHNIQUES IN SUBATOMIC PHYSICS, ASTROPHYSICS, MEDICINE, BIOLOGY AND INDUSTRY, Stockholm, Sweden 24 – 27 June 2003 7. S. Denisov, S. Erin, N. Fedyakin preprint IHEP 99-35, 1999 8. E.Anderssen et al, CERN 99-09 CERN/LHCC/99-03, pp421- 426