Self shielding BG rejection Scintillation Ionization excitationionizationPIDBG rejection

キセノン暗黒物質検出器の売り • Self shielding によるBG rejection • Scintillation とIonizationの両方が検出できる – excitation/ionization比によってPIDしてBG rejection Doke Jpn. J. Appl. Phys. Vol. 41 (2002) NJT Smith ICRC 2013 T 日本物理学会第 69回年次大会 2014年 3月30日 関谷洋之　　　 2

最近のproposal　(様々なmotivation) • Spherical/Cylindrical TPC Masuda, Itow and HS • Paris. TPC conf (2012) Thick GEM in LXe Breskin Paris. TPC conf (2012) PIDに加え、event positionを正確に 決めSelf shieldingを完全なものにする +HV • できれば Cs. I蒸着したGEMで光読み出し Up Level PANDA-X Giboni WPAS 2014 conf. 二相式検出器の液面コントロール が実は厄介だ Charge Detects S 1&S 2 E S 2 Detects S 1 e- -ee S 1 Gas spherical TPC Giomataris JINST 3: P 09007(2008) (GND) HV 日本物理学会第 69回年次大会 2014年 3月30日 関谷洋之 5

キセノン暗黒物質検出器の売り • Self shielding によるBG rejection • Scintillation とIonizationの両方が使える – excitation/ionization比によってPIDしてBG rejection Doke Jpn. J. Appl. Phys. Vol. 41 (2002) Aprile Phys. Rev. Lett 97(2006) LXe 日本物理学会第 69回年次大会 2014年 3月30日 関谷洋之　　　 16

Single-phase TPC Before the realization of two-phase detectors, there were many studies focused on charge amplification and proportional scintillation in single-phase LXe. Derenzo , Phys. Rev. A 9 (1974) 2582 Charge gain ~400 LXe Miyajima NIM 134 (1976) 403 Charge gain ~100 IPMU ACP seminar 7/2/2014 H. Sekiya 17

S 2 in LXe Benetti NIMA 327 (1993) 203 Masuda NIM 160 (1979) 247 109 Cd 22 ke. V was observed Charge gain & proportional scintillation LXe IPMU ACP seminar 7/2/2014 H. Sekiya 18

Why are noble liquids good for WIMP searches? • Large mass/scalability　especially Ar ←cost • Large mass number　 especially Xe →Passive BG rejection: self shielding by fiducialization Noble gas interaction process • Large light yields→low threshold • Purification→low BG • Both scintillation and ionization signals are detectable. • Excitation/ionization ratio provides electron/nuclear recoil separation →Active BG rejection NJT Smith ICRC 2013 T IPMU ACP seminar 7/2/2014 H. Sekiya 19

Single-phase scintillator • This concept has been realized recently – Also sensitive to ionization, in a sense, through the recombination process – Singlet/triplet ratio differs between nuclear/electron recoil events ←possibility of PSD PMT array S 1 Time S 1 IPMU ACP seminar 7/2/2014 PSD? H. Sekiya 20

Single-phase TPC • The original concept, but has not been realized yet. – By applying an electric field, electrons produced by ionization can be collected. These can be observed via charge amplification or proportional scintillation with a strong electric field. Charge +HV E S 2 S 1 - e- e e e- - ee S 1 E -HV S 2 S 1 H. Sekiya Time 21

double-phase TPC • Realized first. Now well-established with several successful implementations – Same as single phase TPC, but if electrons are extracted from liquid phase to gas phase, charge amplification / proportional scintillation become easier with a strong electric field +HV S 2 E S 1 - e- e e -HV S 1 IPMU ACP seminar 7/2/2014 S 2 H. Sekiya Time 22