After Judas betrayed Christ and hanged himself, was he sent to Hell?

It depends how you understand ‘hell’. If ‘hell’ is understood as the Hebrew Sheol first mentioned by Jacob in Genesis 37:35: “I will continue to mourn until I join my son in the grave.” then yes, Sheol, the grave.

But there is a misconception among older Christian church theology, that ‘hell’ is a place of torture and punishment to living souls.  This is not Bible teaching, although graphic symbology is sometimes used in the Bible.  Hell (Hebrew Sheol, Greek Hades) is actually a word for the grave, where dead people are totally dead and know nothing.

Ecclesiastes 9:5-6
For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten.  Also their love, and their hatred, and their envy, is now perished  . . .

So dead people don’t know anything, they don’t love, they don’t hate, they don’t envy – in short, they cease to exist and turn back to dirt.

Ecclesiastes 3:19-20
For what happens to the children of man and what happens to the beasts is the same; as one dies, so dies the other. They all have the same breath, and man has no advantage over the beasts, for all is vanity.  (20)  All go to one place. All are from the dust, and to dust all return.

There is another word sometimes translated “hell fire” “fire of Gehenna” in the New Testament which draws on two sources in the Old Testament. (1) the child sacrifice by idol worshippers in the Ge Henna (Ge Hinnom, wadi Hinnom)  during the time of Jeremiah, and (2) the depiction of the last battle and pile of corpses at the final judgement which is found in the last verse of Isaiah (Isaiah 66:24) which is applied by Jesus in Mark 9:47-48, “worm dies not, fire not quenched” to a future judgement in Ge Hinnom. In fact Isaiah’s last verses originally seen to relate to a prophesied last battle at Har Megiddo (in Greek Armageddon) not to Jeremiah’s Gehenna, but it is possible that Jesus is in Mark 9 wanting to draw the two future events together.

As we can see from the context of Gehenna in Jeremiah 7:31, 19:2–6 and of the fire in Isaiah 66:24, as well as the burning of the weeds (Matthew 13:24–43), the context is not eternal burning torture, but simply permanent destruction. The punishment of the wicked is not to be eternally tortured, but to be eternally excluded from the reward of the righteous – that is, immortality on earth.

2 Thessalonians 1:9-10
They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might,  (10)  when he comes on that day to be glorified in his saints  . . .

The only hope for anyone, is to be resurrected at the return of Jesus to earth.  Those that have known God, will be resurrected and judged – the righteous will be given immortality, the unrighteous will be given eternal destruction.