G.SavianoWorkshop RPC Mumbai February Materials, Filters and Gas analyses for CMS RPC detector in Closed Loop test setup S.Bianco a, A. Brotzu b S.Colafranceschi b, D.Colonna b, F.Felli b, T.Greci c, R.Guida d, L.Passamonti a, D.Pierluigi a, C.Pucci c, A.Russo a, G.Saviano b a Laboratori Nazionali di Frascati dell’INFN, Italy b Laboratori Nazionali di Frascati dell’INFN and Facolta’ di Ingegneria Universita’ degli Studi di Roma“La Sapienza”, Italy c Laboratori Nazionali di Frascati dell’INFN and Scuola di Ingegneria aerospaziale Universita’ degli Studi di Roma“La Sapienza”, Italy d INFN Bari and Universita` degli Studi di Bari, Italy Presented by Giovanna Saviano Laboratori Nazionali di Frascati dell’INFN and Facolta’ di Ingegneria Universita’ degli Studi di Roma “La Sapienza”, Italy

G.SavianoWorkshop RPC Mumbai February CERN Closed Loop Gas System We study the presence of contaminants and their type of accumulation in the Closed Loop Gas system The Closed Loop purifiers are presently used with a 10% fresh mix fraction At the moment, filters must be replaced and regenerated after about days. If not, currents in some of the chambers will increase (R.Guida, Mumbai07).

G.SavianoWorkshop RPC Mumbai February Materials in CERN Closed Loop gas System Bakelite: Melamminic- Phenolic resins+bulk (RPC gaps) Gas: 0.3% SF 6 ; 4.5% C 4 H 10, 96.2% C 2 H 2 F 4 Filters –Molecular Sieve: 5Å Linde type Zeolite –Metallic Filters: Ni Al 2 O 3 ; Cu; CuO-ZnO-Al 2 O 3 Spacers polyvinyl choride C 2 H 3 Cl Cu pipe Steel pipe Plastic tubing

G.SavianoWorkshop RPC Mumbai February Previous studies Bakelite: observed defects with Na and F on RPC gaps exposed at high-radiation –Study of long-term performance of CMS RPC under irradiation at the CERN GIF. M. Abbrescia et al pp. Prepared for 7th Workshop on Resistive Plate Chambers and Related Detectors (RPC2003), Clermont-Ferrand, France, Oct Published in Nucl.Instrum.Meth.A533: ,2004 M. Abbrescia et al. Gas: observed presence of HF in the Closed Loop System –HF production in CMS-Resistive Plate Chambers. M. Abbrescia et al pp. Prepared for 8th Workshop on Resistive Plate Chambers and Related Detectors, Seoul, Korea, Oct Published in Nucl.Phys.Proc.Suppl.158:30-34,2006 M. Abbrescia et al. –Fluoride production in RPCs operated with F-compound gases. G. Aielli, P. Camarri, R. Cardarelli, A. Di Ciaccio, A. Di Simone, B. Liberti, L. Palummo, R. Santonico (INFN, Rome2 & Rome U.,Tor Vergata) pp. Prepared for 8th Workshop on Resistive Plate Chambers and Related Detectors, Seoul, Korea, Oct Published in Nucl.Phys.Proc.Suppl.158: ,2006 G. AielliP. CamarriR. CardarelliA. Di CiaccioA. Di SimoneB. Liberti L. PalummoR. SantonicoINFN, Rome2Rome U.,Tor Vergata

G.SavianoWorkshop RPC Mumbai February Materials sampling oil-less and oiled unused bakelite (chemical analysis) Filters samples at ISR Closed Loop (unused, contaminated, regenerated) have been collected (chemical analysis): –Zeolite –Ni Al 2 O 3; Cu; CuO- ZnO- Al 2 O 3 –Pipes Cu Samples from gaps irradiated at GIF in 2001 (SEM-EDS analysis): –Oiled used bakelite –Oiled used bakelite with defects

G.SavianoWorkshop RPC Mumbai February Trace Elements analyses in filters and bakelite

G.SavianoWorkshop RPC Mumbai February Bakelite plate internal structure paper layer drenched with Melaminic resin Paper bulk drenched with phenolic resin

G.SavianoWorkshop RPC Mumbai February Bakelite SEM-EDS analysis 50x50 cm 2 gap from GIF (test 2001)irradiated at 137 Cs 650 GBq 0,3 mm

G.SavianoWorkshop RPC Mumbai February Observation of Na, F, Cl peaks in sample D Sample CC Sample A Sample D Sample B CC =(cell centre) D=(defect) A=unused oiled bakelite B=unused non oiled bakelite F Na Cl

G.SavianoWorkshop RPC Mumbai February Evidence of NaF in defects (XRD Analysis) XRD analysis with a scanning range between 20° and 100° The crystalline formation, detected in the defected area by the visual inspection, has been identified as NaF NaF distinctive peaks Defect of bakelite Unused bakelite

G.SavianoWorkshop RPC Mumbai February Bakelite trace elements Preliminary analysis of fluxed bakelite shows depletion in trace elements (Cu, As, S) Value %

G.SavianoWorkshop RPC Mumbai February Gas-mix HPLC analyses: contaminants Preliminary analyses on gas show presence of metals in gas-mix 1= blank 2=Fresh mix 3=after gaps 4=after zeolite 5=after metallic filters

G.SavianoWorkshop RPC Mumbai February Filters 1999) Filters designed to remove H 2 O and O ) Several changes in designed parameters (humid mix, etc). Ageing test at GIF showed unidentified peaks in GC. best configuration of filters was: –Zeolite 0.7 CaO. 0.3 Na 2 O. Al 2 O 3. 2 SiO 2. n H 2 O It is especially suitable for the separation of normal- and iso- paraffins, in PSA hydrogen purification and in oxygen concentrators. It is an excellent adsorbent to remove H 2 O, CO 2, H 2 S from sour natural gas streams, minimising COS formation. Light mercaptans are also adsorbed. –Cu-Zn filter type R3-12 from BASF (25%) designed for removal of arsine, phosphine, H 2 S and COS. R 3-12 is widely used in the purification of polymer grade propylene, and to protect noble metal catalysts from arsenic and sulphur –Cu filter type R3-11G from BASF (25%) designed for regenerative removal of O 2, CO, H 2 and others from industrial gases and liquids. –Ni-Al 2 O 3 filter type 6525 from Leuna (50%)

G.SavianoWorkshop RPC Mumbai February XRD pattern of molecular sieve matches Linde Type A zeolite XRD performed at University of Rome “La Sapienza” on a sample of unused zeolite. On the right, the reference pattern for standard Linde Type A zeolite. REFERENCE

G.SavianoWorkshop RPC Mumbai February Type 5Å zeolites from Zeochem Two Mechanisms: –Molecular sieve –Ion exchange Pore dimensions 3A (3 Å, K) 4A (4 Å, Na) 5A (5 Å, Ca) Framework of Linde Type A zeolites Anionic framework

G.SavianoWorkshop RPC Mumbai February Zeolite captures F, regeneration does not fully desorb zeolite (right) Gas-mix tend to leach SiO 2 and Al 2 O 3 i.e. the “framework” of zeolite (left) Values in %

G.SavianoWorkshop RPC Mumbai February Pollutants in Zeolite Zeolite acts as good metals filter, but desorbtion is not complete for Ni and F

G.SavianoWorkshop RPC Mumbai February Pollutants in Metallic Filters Ni-Al 2 O 3 Filters tend to release Cu and Cr during filtering Both metallic Filtres capture F and S but the regeneration does not desorb them

G.SavianoWorkshop RPC Mumbai February Conclusions: Bakelite Bakelite shows a depletion in some trace elements ( Cu, Ni, As, Cr,Sb) after flux. Where do they go? Part of them are adsorbed in zeolite (Cu, Ni) We have shown how defects in fluxed bakelite have a crystalline structure, identified as NaF

G.SavianoWorkshop RPC Mumbai February Conclusions: gas HPLC preliminary analysis reveals the presence of extra-pollutants in gas (metals and F - ) It is of paramount importance to analyze gas in different points of CL

G.SavianoWorkshop RPC Mumbai February Conclusions: zeolite Zeolite captures F, Cu, Ni, S but regeneration does not fully desorb zeolite Gas-mix (due to the presence of HF) tends to leach SiO 2 and Al 2 O 3 i.e. the “framework” of zeolite. Chemical analyses show a depletion in Si, Al contents zeolite acts as a buffer for pH (from 4.5 to 7 ) see R.Guida, this Conference

G.SavianoWorkshop RPC Mumbai February Conclusions: Filters Ni-Al 2 O 3 Ni-Al 2 O 3 filters release Cu and Cr during filtration. They capture F and S, but regeneration does not desorb filters Cu; CuO-ZnO-Al 2 O 3 S can easily form Cu and Zn sulphide, difficult to remove from filters Both metallic filtres capture F and S but the regeneration does not desorb them completely

G.SavianoWorkshop RPC Mumbai February Conclusions: Filters Regeneration Cu; CuO-ZnO and Ni-Al 2 O 3 are declared as not regenerable (BASF catalyst technical bulletin) Both filters undergo regeneration at 200°C under Ar/H 2 for 12 hours As and S react with the Cu and Zn constituents in the catalyst to form stable metal complexes which do not migrate or desorb off of the catalyst. It is important to characterize the filters (metallic, zeolite) in order to understand their selective absorbtion and ion-exchange possibility, their life time (in function of the complex system at CL) and eventually it is of PARAMOUNT importance to set up a specific desorbtion procedure

G.SavianoWorkshop RPC Mumbai February CONCLUSIONS AND OUTLOOK The system is very complex. Many different chemical compositions in the system components. The presence of F compounds in gas-mix damages some af them. These results are preliminary. We need different operating procedures for studying the filters kinetic and customize best desorbtion process. Although filters need to be chemically characterized, the set-up currently used is able to operate correctly the CMS-RPC detector. SEM-EDS analyses are currently in progress on bakelite We are setting up a new procedure for analyses on gas at ISR